diff --git a/src/core/sys/windows/mmsystem.d b/src/core/sys/windows/mmsystem.d
diff --git a/src/core/sys/windows/ntsecpkg.d b/src/core/sys/windows/ntsecpkg.d
@@ -180,8 +180,8 @@ alias void function(ULONG_PTR, ULONG_PTR, PSecBuffer,
 
 /* misc typedefs used in the below prototypes */
 alias PVOID* PLSA_CLIENT_REQUEST;
-alias ULONG LSA_SEC_HANDLE;
-alias ULONG* PLSA_SEC_HANDLE;
+alias ULONG_PTR LSA_SEC_HANDLE;
+alias LSA_SEC_HANDLE* PLSA_SEC_HANDLE;
 alias LPTHREAD_START_ROUTINE SEC_THREAD_START;
 alias PSECURITY_ATTRIBUTES SEC_ATTRS;
 

diff --git a/src/core/sys/windows/oaidl.d b/src/core/sys/windows/oaidl.d
@@ -331,7 +331,7 @@ struct PARAMDESC {
 alias PARAMDESC* LPPARAMDESC;
 
 struct IDLDESC {
-    ULONG dwReserved;
+    ULONG_PTR dwReserved;
     USHORT wIDLFlags;
 }
 alias IDLDESC* LPIDLDESC;

diff --git a/src/core/sys/windows/ole.d b/src/core/sys/windows/ole.d
@@ -156,7 +156,7 @@ enum OLEOPT_UPDATE {
 }
 
 mixin DECLARE_HANDLE!("HOBJECT");
-alias LONG LHSERVER, LHCLIENTDOC, LHSERVERDOC;
+alias LONG_PTR LHSERVER, LHCLIENTDOC, LHSERVERDOC;
 
 struct OLEOBJECTVTBL {
     extern (Windows) {

diff --git a/src/core/sys/windows/oleidl.d b/src/core/sys/windows/oleidl.d
@@ -230,11 +230,11 @@ interface IDropTarget : IUnknown {
 alias IDropTarget LPDROPTARGET;
 
 extern (Windows) {
-    alias BOOL function(DWORD) __IView_pfncont;
+    alias BOOL function(ULONG_PTR) __IView_pfncont;
 }
 
 interface IViewObject : IUnknown {
-    HRESULT Draw(DWORD,LONG,PVOID,DVTARGETDEVICE*,HDC,HDC,LPCRECTL,LPCRECTL,__IView_pfncont pfnContinue,DWORD);
+    HRESULT Draw(DWORD,LONG,PVOID,DVTARGETDEVICE*,HDC,HDC,LPCRECTL,LPCRECTL,__IView_pfncont pfnContinue,ULONG_PTR);
     HRESULT GetColorSet(DWORD,LONG,PVOID,DVTARGETDEVICE*,HDC,LPLOGPALETTE*);
     HRESULT Freeze(DWORD,LONG,PVOID,PDWORD);
     HRESULT Unfreeze(DWORD);

diff --git a/src/core/sys/windows/prsht.d b/src/core/sys/windows/prsht.d
@@ -335,8 +335,8 @@ extern (Windows) {
     HPROPSHEETPAGE CreatePropertySheetPageA(LPCPROPSHEETPAGEA);
     HPROPSHEETPAGE CreatePropertySheetPageW(LPCPROPSHEETPAGEW);
     BOOL DestroyPropertySheetPage(HPROPSHEETPAGE);
-    int PropertySheetA(LPCPROPSHEETHEADERA);
-    int PropertySheetW(LPCPROPSHEETHEADERW);
+    INT_PTR PropertySheetA(LPCPROPSHEETHEADERA);
+    INT_PTR PropertySheetW(LPCPROPSHEETHEADERW);
 }
 
 version (Unicode) {

diff --git a/src/core/sys/windows/rasdlg.d b/src/core/sys/windows/rasdlg.d
@@ -78,8 +78,8 @@ alias RASDIALDLG* LPRASDIALDLG;
 
 // Application-defined callback functions
 extern (Windows) {
-    alias VOID function(DWORD, DWORD, LPWSTR, LPVOID) RASPBDLGFUNCW;
-    alias VOID function(DWORD, DWORD, LPSTR, LPVOID) RASPBDLGFUNCA;
+    alias VOID function(ULONG_PTR, DWORD, LPWSTR, LPVOID) RASPBDLGFUNCW;
+    alias VOID function(ULONG_PTR, DWORD, LPSTR, LPVOID) RASPBDLGFUNCA;
 }
 
 struct RASPBDLGA {

diff --git a/src/core/sys/windows/rpcdcep.d b/src/core/sys/windows/rpcdcep.d
@@ -63,7 +63,7 @@ alias void function (PRPC_MESSAGE Message) RPC_DISPATCH_FUNCTION;
 struct RPC_DISPATCH_TABLE {
     uint DispatchTableCount;
     RPC_DISPATCH_FUNCTION* DispatchTable;
-    int  Reserved;
+    LONG_PTR Reserved;
 }
 alias RPC_DISPATCH_TABLE* PRPC_DISPATCH_TABLE;
 
@@ -92,7 +92,7 @@ struct RPC_CLIENT_INTERFACE {
     PRPC_DISPATCH_TABLE   DispatchTable;
     uint                  RpcProtseqEndpointCount;
     PRPC_PROTSEQ_ENDPOINT RpcProtseqEndpoint;
-    uint                  Reserved;
+    ULONG_PTR             Reserved;
 const(void)*          InterpreterInfo;
 }
 alias RPC_CLIENT_INTERFACE* PRPC_CLIENT_INTERFACE;

diff --git a/src/core/sys/windows/rpcndr.d b/src/core/sys/windows/rpcndr.d
@@ -74,9 +74,9 @@ enum cbNDRContext=20;
 //MACRO #define _midl_unma2( p, cast ) *(( cast *)p)++
 //MACRO #define _midl_unma3( p, cast ) *(( cast *)p)++
 //MACRO #define _midl_unma4( p, cast ) *(( cast *)p)++
-//MACRO #define _midl_fa2( p ) (p = (RPC_BUFPTR )((unsigned long)(p+1) & 0xfffffffe))
-//MACRO #define _midl_fa4( p ) (p = (RPC_BUFPTR )((unsigned long)(p+3) & 0xfffffffc))
-//MACRO #define _midl_fa8( p ) (p = (RPC_BUFPTR )((unsigned long)(p+7) & 0xfffffff8))
+//MACRO #define _midl_fa2( p ) (p = (RPC_BUFPTR )((LONG_PTR)(p+1) & 0xffffffff_fffffffe))
+//MACRO #define _midl_fa4( p ) (p = (RPC_BUFPTR )((LONG_PTR)(p+3) & 0xffffffff_fffffffc))
+//MACRO #define _midl_fa8( p ) (p = (RPC_BUFPTR )((LONG_PTR)(p+7) & 0xffffffff_fffffff8))
 //MACRO #define _midl_addp( p, n ) (p += n)
 //MACRO #define _midl_marsh_lhs( p, cast ) *(*( cast **)&p)++
 //MACRO #define _midl_marsh_up( mp, p ) *(*(unsigned long **)&mp)++ = (unsigned long)p
@@ -92,7 +92,7 @@ enum cbNDRContext=20;
 //MACRO #define NdrUnMarshSCtxtHdl(pc, p,drep) (pc = NdrSContextUnMarshall(p,drep ))
 //MACRO #define NdrMarshSCtxtHdl(pc,p,rd) (NdrSContextMarshall((NDR_SCONTEXT)pc,p, (NDR_RUNDOWN)rd)
 
-//MACRO #define NdrFieldOffset(s,f) (long)(& (((s *)0)->f))
+//MACRO #define NdrFieldOffset(s,f) (LONG_PTR)(& (((s *)0)->f))
 //MACRO #define NdrFieldPad(s,f,p,t) (NdrFieldOffset(s,f) - NdrFieldOffset(s,p) - sizeof(t))
 //MACRO #define NdrFcShort(s) (unsigned char)(s & 0xff), (unsigned char)(s >> 8)
 //MACRO #define NdrFcLong(s) (unsigned char)(s & 0xff), (unsigned char)((s & 0x0000ff00) >> 8), (unsigned char)((s & 0x00ff0000) >> 16), (unsigned char)(s >> 24)
@@ -180,7 +180,7 @@ struct MIDL_STUB_MESSAGE {
     ubyte *PointerBufferMark;
     ubyte fBufferValid;
     ubyte Unused;
-    uint MaxCount;
+    ULONG_PTR MaxCount;
     uint Offset;
     uint ActualCount;
     void* function (uint) pfnAllocate;
@@ -210,7 +210,7 @@ const(_MIDL_STUB_DESC)* StubDesc;
     uint * SizePtrLengthArray;
     void* pArgQueue;
     uint dwStubPhase;
-    uint[5] w2kReserved;
+    INT_PTR[5] w2kReserved;
 }
 alias MIDL_STUB_MESSAGE * PMIDL_STUB_MESSAGE;
 
@@ -337,7 +337,7 @@ alias MIDL_STUBLESS_PROXY_INFO *PMIDL_STUBLESS_PROXY_INFO;
 
 union CLIENT_CALL_RETURN {
     void *Pointer;
-    int Simple;
+    LONG_PTR Simple;
 }
 
 enum XLAT_SIDE {

diff --git a/src/core/sys/windows/shellapi.d b/src/core/sys/windows/shellapi.d
@@ -357,7 +357,7 @@ extern (Windows) nothrow @nogc {
     UINT ExtractIconExW(LPCWSTR, int, HICON*, HICON*, UINT);
     HINSTANCE FindExecutableA(LPCSTR, LPCSTR, LPSTR);
     HINSTANCE FindExecutableW(LPCWSTR, LPCWSTR, LPWSTR);
-    UINT SHAppBarMessage(DWORD, PAPPBARDATA);
+    UINT_PTR SHAppBarMessage(DWORD, PAPPBARDATA);
     BOOL Shell_NotifyIconA(DWORD, PNOTIFYICONDATAA);
     BOOL Shell_NotifyIconW(DWORD, PNOTIFYICONDATAW);
     int ShellAboutA(HWND, LPCSTR, LPCSTR, HICON);
@@ -369,8 +369,8 @@ extern (Windows) nothrow @nogc {
     int SHFileOperationA(LPSHFILEOPSTRUCTA);
     int SHFileOperationW(LPSHFILEOPSTRUCTW);
     void SHFreeNameMappings(HANDLE);
-    DWORD SHGetFileInfoA(LPCSTR, DWORD, SHFILEINFOA*, UINT, UINT);
-    DWORD SHGetFileInfoW(LPCWSTR, DWORD, SHFILEINFOW*, UINT, UINT);
+    DWORD_PTR SHGetFileInfoA(LPCSTR, DWORD, SHFILEINFOA*, UINT, UINT);
+    DWORD_PTR SHGetFileInfoW(LPCWSTR, DWORD, SHFILEINFOW*, UINT, UINT);
     HRESULT SHQueryRecycleBinA(LPCSTR,  LPSHQUERYRBINFO);
     HRESULT SHQueryRecycleBinW(LPCWSTR,  LPSHQUERYRBINFO);
     HRESULT SHEmptyRecycleBinA(HWND, LPCSTR, DWORD);

diff --git a/src/core/sys/windows/shlobj.d b/src/core/sys/windows/shlobj.d
@@ -683,7 +683,7 @@ interface IObjMgr : IUnknown {
 interface IContextMenu : IUnknown {
     HRESULT QueryContextMenu(HMENU, UINT, UINT, UINT, UINT);
     HRESULT InvokeCommand(LPCMINVOKECOMMANDINFO);
-    HRESULT GetCommandString(UINT, UINT, PUINT, LPSTR, UINT);
+    HRESULT GetCommandString(UINT_PTR, UINT, PUINT, LPSTR, UINT);
 }
 alias IContextMenu LPCONTEXTMENU;
 

diff --git a/src/core/sys/windows/winbase.d b/src/core/sys/windows/winbase.d
@@ -1863,7 +1863,7 @@ WINBASEAPI DWORD WINAPI GetCurrentThreadId(void);
     BOOL GetPrivateProfileStructA(LPCSTR, LPCSTR, LPVOID, UINT, LPCSTR);
     BOOL GetPrivateProfileStructW(LPCWSTR, LPCWSTR, LPVOID, UINT, LPCWSTR);
     FARPROC GetProcAddress(HMODULE, LPCSTR); // 1st param wrongly HINSTANCE in MinGW
-    BOOL GetProcessAffinityMask(HANDLE, PDWORD, PDWORD);
+    BOOL GetProcessAffinityMask(HANDLE, PDWORD_PTR, PDWORD_PTR);
     DWORD GetProcessVersion(DWORD);
     UINT GetProfileIntA(LPCSTR, LPCSTR, INT);
     UINT GetProfileIntW(LPCWSTR, LPCWSTR, INT);

diff --git a/src/core/sys/windows/wincrypt.d b/src/core/sys/windows/wincrypt.d
@@ -501,7 +501,7 @@ enum {
 
 
 alias UINT ALG_ID;
-alias ULONG HCRYPTPROV, HCRYPTKEY, HCRYPTHASH;
+alias ULONG_PTR HCRYPTPROV, HCRYPTKEY, HCRYPTHASH;
 alias PVOID HCERTSTORE, HCRYPTMSG, HCERTCHAINENGINE;
 
 struct VTableProvStruc {
@@ -844,7 +844,7 @@ const(void)*, PCCERT_CHAIN_CONTEXT);
     BOOL CryptAcquireContextA(HCRYPTPROV*, LPCSTR, LPCSTR, DWORD, DWORD);
     BOOL CryptAcquireContextW(HCRYPTPROV*, LPCWSTR, LPCWSTR, DWORD, DWORD);
      BOOL CryptContextAddRef(HCRYPTPROV, DWORD*, DWORD);
-    BOOL CryptReleaseContext(HCRYPTPROV, DWORD);
+    BOOL CryptReleaseContext(HCRYPTPROV, ULONG_PTR);
     BOOL CryptGenKey(HCRYPTPROV, ALG_ID, DWORD, HCRYPTKEY*);
     BOOL CryptDeriveKey(HCRYPTPROV, ALG_ID, HCRYPTHASH, DWORD, HCRYPTKEY*);
     BOOL CryptDestroyKey(HCRYPTKEY);

diff --git a/src/core/sys/windows/wingdi.d b/src/core/sys/windows/wingdi.d
@@ -2465,7 +2465,7 @@ alias EMRBITBLT* PEMRBITBLT;
 struct LOGBRUSH {
     UINT     lbStyle;
     COLORREF lbColor;
-    LONG     lbHatch;
+    ULONG_PTR lbHatch;
 }
 alias TypeDef!(LOGBRUSH) PATTERN;
 alias LOGBRUSH* PLOGBRUSH, NPLOGBRUSH, LPLOGBRUSH;

diff --git a/src/core/sys/windows/wininet.d b/src/core/sys/windows/wininet.d
@@ -647,7 +647,7 @@ enum INTERNET_SCHEME {
 alias INTERNET_SCHEME* LPINTERNET_SCHEME;
 
 struct INTERNET_ASYNC_RESULT {
-    DWORD dwResult;
+    DWORD_PTR dwResult;
     DWORD dwError;
 }
 alias INTERNET_ASYNC_RESULT* LPINTERNET_ASYNC_RESULT;
@@ -721,7 +721,7 @@ struct INTERNET_CERTIFICATE_INFO {
 }
 alias INTERNET_CERTIFICATE_INFO* LPINTERNET_CERTIFICATE_INFO;
 
-extern (Windows) alias void function(HINTERNET, DWORD, DWORD, PVOID, DWORD)
+extern (Windows) alias void function(HINTERNET, DWORD_PTR, DWORD, PVOID, DWORD)
   INTERNET_STATUS_CALLBACK;
 alias INTERNET_STATUS_CALLBACK* LPINTERNET_STATUS_CALLBACK;
 
@@ -986,17 +986,17 @@ extern (Windows) {
     HINTERNET InternetOpenW(LPCWSTR, DWORD, LPCWSTR, LPCWSTR, DWORD);
     BOOL InternetCloseHandle(HINTERNET);
     HINTERNET InternetConnectA(HINTERNET, LPCSTR, INTERNET_PORT, LPCSTR,
-      LPCSTR, DWORD, DWORD, DWORD);
+      LPCSTR, DWORD, DWORD, DWORD_PTR);
     HINTERNET InternetConnectW(HINTERNET, LPCWSTR, INTERNET_PORT, LPCWSTR,
-      LPCWSTR, DWORD, DWORD, DWORD);
+      LPCWSTR, DWORD, DWORD, DWORD_PTR);
     HINTERNET InternetOpenUrlA(HINTERNET, LPCSTR, LPCSTR, DWORD, DWORD,
-      DWORD);
+      DWORD_PTR);
     HINTERNET InternetOpenUrlW(HINTERNET, LPCWSTR, LPCWSTR, DWORD, DWORD,
-      DWORD);
+      DWORD_PTR);
     BOOL InternetReadFile(HINTERNET, PVOID, DWORD, PDWORD);
-    DWORD InternetSetFilePointer(HINTERNET, LONG, PVOID, DWORD, DWORD);
+    DWORD InternetSetFilePointer(HINTERNET, LONG, PVOID, DWORD, DWORD_PTR);
     BOOL InternetWriteFile(HINTERNET, LPCVOID, DWORD, PDWORD);
-    BOOL InternetQueryDataAvailable(HINTERNET, PDWORD, DWORD, DWORD);
+    BOOL InternetQueryDataAvailable(HINTERNET, PDWORD, DWORD, DWORD_PTR);
     BOOL InternetFindNextFileA(HINTERNET, PVOID);
     BOOL InternetFindNextFileW(HINTERNET, PVOID);
     BOOL InternetQueryOptionA(HINTERNET, DWORD, PVOID, PDWORD);
@@ -1010,20 +1010,20 @@ extern (Windows) {
     INTERNET_STATUS_CALLBACK InternetSetStatusCallback(HINTERNET,
       INTERNET_STATUS_CALLBACK);
     DWORD FtpGetFileSize(HINTERNET, LPDWORD);
-    HINTERNET FtpFindFirstFileA(HINTERNET, LPCSTR, LPWIN32_FIND_DATA, DWORD,
-      DWORD);
-    HINTERNET FtpFindFirstFileW(HINTERNET, LPCWSTR, LPWIN32_FIND_DATA, DWORD,
-      DWORD);
-    BOOL FtpGetFileA(HINTERNET, LPCSTR, LPCSTR, BOOL, DWORD, DWORD, DWORD);
-    BOOL FtpGetFileW(HINTERNET, LPCWSTR, LPCWSTR, BOOL, DWORD, DWORD, DWORD);
-    BOOL FtpPutFileA(HINTERNET, LPCSTR, LPCSTR, DWORD, DWORD);
-    BOOL FtpPutFileW(HINTERNET, LPCWSTR, LPCWSTR, DWORD, DWORD);
+    HINTERNET FtpFindFirstFileA(HINTERNET, LPCSTR, LPWIN32_FIND_DATAA, DWORD,
+      DWORD_PTR);
+    HINTERNET FtpFindFirstFileW(HINTERNET, LPCWSTR, LPWIN32_FIND_DATAW, DWORD,
+      DWORD_PTR);
+    BOOL FtpGetFileA(HINTERNET, LPCSTR, LPCSTR, BOOL, DWORD, DWORD, DWORD_PTR);
+    BOOL FtpGetFileW(HINTERNET, LPCWSTR, LPCWSTR, BOOL, DWORD, DWORD, DWORD_PTR);
+    BOOL FtpPutFileA(HINTERNET, LPCSTR, LPCSTR, DWORD, DWORD_PTR);
+    BOOL FtpPutFileW(HINTERNET, LPCWSTR, LPCWSTR, DWORD, DWORD_PTR);
     BOOL FtpDeleteFileA(HINTERNET, LPCSTR);
     BOOL FtpDeleteFileW(HINTERNET, LPCWSTR);
     BOOL FtpRenameFileA(HINTERNET, LPCSTR, LPCSTR);
     BOOL FtpRenameFileW(HINTERNET, LPCWSTR, LPCWSTR);
-    HINTERNET FtpOpenFileA(HINTERNET, LPCSTR, DWORD, DWORD, DWORD);
-    HINTERNET FtpOpenFileW(HINTERNET, LPCWSTR, DWORD, DWORD, DWORD);
+    HINTERNET FtpOpenFileA(HINTERNET, LPCSTR, DWORD, DWORD, DWORD_PTR);
+    HINTERNET FtpOpenFileW(HINTERNET, LPCWSTR, DWORD, DWORD, DWORD_PTR);
     BOOL FtpCreateDirectoryA(HINTERNET, LPCSTR);
     BOOL FtpCreateDirectoryW(HINTERNET, LPCWSTR);
     BOOL FtpRemoveDirectoryA(HINTERNET, LPCSTR);
@@ -1041,19 +1041,19 @@ extern (Windows) {
     BOOL GopherGetLocatorTypeA(LPCSTR, PDWORD);
     BOOL GopherGetLocatorTypeW(LPCWSTR, PDWORD);
     HINTERNET GopherFindFirstFileA(HINTERNET, LPCSTR, LPCSTR,
-      LPGOPHER_FIND_DATAA, DWORD, DWORD);
+      LPGOPHER_FIND_DATAA, DWORD, DWORD_PTR);
     HINTERNET GopherFindFirstFileW(HINTERNET, LPCWSTR, LPCWSTR,
-      LPGOPHER_FIND_DATAW, DWORD, DWORD);
-    HINTERNET GopherOpenFileA(HINTERNET, LPCSTR, LPCSTR, DWORD, DWORD);
-    HINTERNET GopherOpenFileW(HINTERNET, LPCWSTR, LPCWSTR, DWORD, DWORD);
+      LPGOPHER_FIND_DATAW, DWORD, DWORD_PTR);
+    HINTERNET GopherOpenFileA(HINTERNET, LPCSTR, LPCSTR, DWORD, DWORD_PTR);
+    HINTERNET GopherOpenFileW(HINTERNET, LPCWSTR, LPCWSTR, DWORD, DWORD_PTR);
     BOOL GopherGetAttributeA(HINTERNET, LPCSTR, LPCSTR, LPBYTE, DWORD,
-      PDWORD, GOPHER_ATTRIBUTE_ENUMERATOR, DWORD);
+      PDWORD, GOPHER_ATTRIBUTE_ENUMERATOR, DWORD_PTR);
     BOOL GopherGetAttributeW(HINTERNET, LPCWSTR, LPCWSTR, LPBYTE, DWORD,
-      PDWORD, GOPHER_ATTRIBUTE_ENUMERATOR, DWORD);
+      PDWORD, GOPHER_ATTRIBUTE_ENUMERATOR, DWORD_PTR);
     HINTERNET HttpOpenRequestA(HINTERNET, LPCSTR, LPCSTR, LPCSTR, LPCSTR,
-      LPCSTR*, DWORD, DWORD);
+      LPCSTR*, DWORD, DWORD_PTR);
     HINTERNET HttpOpenRequestW(HINTERNET, LPCWSTR, LPCWSTR, LPCWSTR, LPCWSTR,
-      LPCWSTR*, DWORD, DWORD);
+      LPCWSTR*, DWORD, DWORD_PTR);
     BOOL HttpAddRequestHeadersA(HINTERNET, LPCSTR, DWORD, DWORD);
     BOOL HttpAddRequestHeadersW(HINTERNET, LPCWSTR, DWORD, DWORD);
     BOOL HttpSendRequestA(HINTERNET, LPCSTR, DWORD, PVOID, DWORD);
@@ -1099,13 +1099,13 @@ extern (Windows) {
     DWORD AuthenticateUser(PVOID*, LPSTR, LPSTR, DWORD, LPSTR, DWORD, LPSTR,
       LPSTR);
     BOOL HttpSendRequestExA(HINTERNET, LPINTERNET_BUFFERSA,
-      LPINTERNET_BUFFERSA, DWORD, DWORD);
+      LPINTERNET_BUFFERSA, DWORD, DWORD_PTR);
     BOOL HttpSendRequestExW(HINTERNET, LPINTERNET_BUFFERSW,
-      LPINTERNET_BUFFERSW, DWORD, DWORD);
-    BOOL HttpEndRequestA(HINTERNET, LPINTERNET_BUFFERSA, DWORD, DWORD);
-    BOOL HttpEndRequestW(HINTERNET, LPINTERNET_BUFFERSW, DWORD, DWORD);
+      LPINTERNET_BUFFERSW, DWORD, DWORD_PTR);
+    BOOL HttpEndRequestA(HINTERNET, LPINTERNET_BUFFERSA, DWORD, DWORD_PTR);
+    BOOL HttpEndRequestW(HINTERNET, LPINTERNET_BUFFERSW, DWORD, DWORD_PTR);
     DWORD InternetDial(HWND, LPTSTR, DWORD, LPDWORD, DWORD);
-    DWORD InternetHangUp(DWORD, DWORD);
+    DWORD InternetHangUp(DWORD_PTR, DWORD);
     BOOL InternetGoOnline(LPTSTR, HWND, DWORD);
     BOOL InternetAutodial(DWORD, DWORD);
     BOOL InternetAutodialHangup(DWORD);

diff --git a/src/core/sys/windows/winldap.d b/src/core/sys/windows/winldap.d
@@ -278,8 +278,15 @@ enum {
     LDAP_SUBSTRING_FINAL
 }
 
+// should be opaque structure
 struct LDAP {
-    char[76] Reserved;
+    struct _ld_sp {
+        UINT_PTR sb_sd;
+        UCHAR[(10*ULONG.sizeof)+1] Reserved1;
+        ULONG_PTR sb_naddr;
+        UCHAR[(6*ULONG.sizeof)] Reserved2;
+    }
+    _ld_sp   ld_sp;
     PCHAR    ld_host;
     ULONG    ld_version;
     UCHAR    ld_lberoptions;
@@ -292,6 +299,7 @@ struct LDAP {
 }
 alias LDAP* PLDAP;
 
+// should be opaque structure
 struct LDAPMessage {
     ULONG        lm_msgid;
     ULONG        lm_msgtype;

diff --git a/src/core/sys/windows/winnetwk.d b/src/core/sys/windows/winnetwk.d
@@ -288,7 +288,7 @@ struct NETINFOSTRUCT {
     DWORD dwProviderVersion;
     DWORD dwStatus;
     DWORD dwCharacteristics;
-    DWORD dwHandle;
+    ULONG_PTR dwHandle;
     WORD  wNetType;
     DWORD dwPrinters;
     DWORD dwDrives;

diff --git a/src/core/sys/windows/winperf.d b/src/core/sys/windows/winperf.d
@@ -104,9 +104,17 @@ struct PERF_OBJECT_TYPE {
     DWORD DefinitionLength;
     DWORD HeaderLength;
     DWORD ObjectNameTitleIndex;
+version (Win64) {
+    DWORD ObjectNameTitle;
+} else {
     LPWSTR ObjectNameTitle;
+}
     DWORD ObjectHelpTitleIndex;
+version (Win64) {
+    DWORD ObjectHelpTitle;
+} else {
     LPWSTR ObjectHelpTitle;
+}
     DWORD DetailLevel;
     DWORD NumCounters;
     LONG DefaultCounter;
@@ -120,9 +128,17 @@ alias PERF_OBJECT_TYPE * PPERF_OBJECT_TYPE;
 struct PERF_COUNTER_DEFINITION {
     DWORD ByteLength;
     DWORD CounterNameTitleIndex;
+version (Win64) {
+    DWORD CounterNameTitle;
+} else {
     LPWSTR CounterNameTitle;
+}
     DWORD CounterHelpTitleIndex;
+version (Win64) {
+    DWORD CounterHelpTitle;
+} else {
     LPWSTR CounterHelpTitle;
+}
     LONG DefaultScale;
     DWORD DetailLevel;
     DWORD CounterType;

diff --git a/src/core/sys/windows/winuser.d b/src/core/sys/windows/winuser.d
@@ -2877,7 +2877,7 @@ struct HELPINFO {
     int iContextType;
     int iCtrlId;
     HANDLE hItemHandle;
-    DWORD dwContextId;
+    DWORD_PTR dwContextId;
     POINT MousePos;
 }
 alias HELPINFO* LPHELPINFO;
@@ -3184,7 +3184,7 @@ struct DROPSTRUCT {
     HWND hwndSource;
     HWND hwndSink;
     DWORD wFmt;
-    DWORD dwData;
+    ULONG_PTR dwData;
     POINT ptDrop;
     DWORD dwControlData;
 }
@@ -3730,7 +3730,7 @@ BOOL DlgDirSelectComboBoxExW(HWND, LPWSTR, int, int);
 BOOL DlgDirSelectExA(HWND, LPSTR, int, int);
 BOOL DlgDirSelectExW(HWND, LPWSTR, int, int);
 BOOL DragDetect(HWND, POINT);
-DWORD DragObject(HWND, HWND, UINT, DWORD, HCURSOR);
+DWORD DragObject(HWND, HWND, UINT, ULONG_PTR, HCURSOR);
 BOOL DrawAnimatedRects(HWND, int, LPCRECT, LPCRECT);
 BOOL DrawCaption(HWND, HDC, LPCRECT, UINT);
 BOOL DrawEdge(HDC, LPRECT, UINT, UINT);
@@ -4144,8 +4144,8 @@ BOOL WaitMessage();
 HWND WindowFromDC(HDC hDC);
 HWND WindowFromPoint(POINT);
 UINT WinExec(LPCSTR, UINT);
-BOOL WinHelpA(HWND, LPCSTR, UINT, DWORD);
-BOOL WinHelpW(HWND, LPCWSTR, UINT, DWORD);
+BOOL WinHelpA(HWND, LPCSTR, UINT, ULONG_PTR);
+BOOL WinHelpW(HWND, LPCWSTR, UINT, ULONG_PTR);
 
 extern (C) {
     int wsprintfA(LPSTR, LPCSTR, ...);