diff --git a/IfKeyExists.nsh b/IfKeyExists.nsh
new file mode 100644
index 0000000..5b95665
--- /dev/null
+++ b/IfKeyExists.nsh
@@ -0,0 +1,27 @@
+!include LogicLib.nsh
+!macro IfKeyExists ROOT MAIN_KEY KEY
+  Push $R0
+  Push $R1
+  Push $R2
+ 
+  # XXX bug if ${ROOT}, ${MAIN_KEY} or ${KEY} use $R0 or $R1
+ 
+  StrCpy $R1 "0" # loop index
+  StrCpy $R2 "0" # not found
+ 
+  ${Do}
+    EnumRegKey $R0 ${ROOT} "${MAIN_KEY}" "$R1"
+    ${If} $R0 == "${KEY}"
+      StrCpy $R2 "1" # found
+      ${Break}
+    ${EndIf}
+    IntOp $R1 $R1 + 1
+  ${LoopWhile} $R0 != ""
+ 
+  ClearErrors
+ 
+  Exch 2
+  Pop $R0
+  Pop $R1
+  Exch $R2
+!macroend
diff --git a/Makefile b/Makefile
index d6d3b85..425de6e 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-NSIS=/cygdrive/c/Program\ Files\ \(x86\)/NSIS/makensisw.exe
+NSIS=/cygdrive/c/Program\ Files\ \(x86\)/NSIS/makensis.exe
 SCRIPT=install.nsi
 OCAMLROOT=/cygdrive/c/ocamlmgw/
 OCAMLROOTW=c:/ocamlmgw/