Hopefully this adds the .NET prerequisite installation.

.gitignore

@@ -6,6 +6,7 @@ MSWindows/FFMPEGWrapper.suo
 Mac/build/
 *.pyc
 *.pfx
+*~
 pcfpfxpassword.yaml
 Mac/DMG/*.dmg
 /Mac/Miro Video Converter.xcodeproj/*.pbxuser

MSWindows/DotNet.nsh

@@ -0,0 +1,189 @@
+# DotNET and MSI version checking macro.
+# Written by AnarkiNet(AnarkiNet@gmail.com) originally
+# modified by eyal0 in 2007 and sevenalive in 2010
+# Installs the Microsoft .NET Framework version 3.5 SP1 if the required .NET runtime is not installed
+# To use, call the macro with a string:
+# Example: non real version numbers
+#   !insertmacro CheckDotNET 3.5
+#   !insertmacro CheckDotNET 3.5sp1
+# (Version 2.0.9 is less than version 2.0.10.)
+# Example: latest real version number at time of writing
+# !insertmacro CheckDotNET "2.0.50727"
+# All register variables are saved and restored by CheckDotNet
+# No output
+ Var DN3Dir
+ Var dotnet3 ; is .NET 3 installed?
+ Var dotnet35 ; is .NET 3.5 installed?
+ Var dotnet35ver ; 3.5 version
+ Var dotnet35sp1 ; sp1
+!macro CheckDotNET DotNetReqVer
+  !define DOTNET_URL "http://download.microsoft.com/download/2/0/e/20e90413-712f-438c-988e-fdaa79a8ac3d/dotnetfx35.exe"
+  DetailPrint "Checking your .NET Framework version..."
+  Push $0
+  Push $1
+  Push $2
+  Push $3
+  Push $4
+  Push $5
+  Push $6 ;backup of intsalled ver
+  Push $7 ;backup of DoNetReqVer
+
+# NSIS
+
+  ReadRegStr $dotnet3 HKEY_LOCAL_MACHINE "Software\Microsoft\NET Framework Setup\NDP\v3.0\Setup" "InstallSuccess"
+  ReadRegStr $dotnet35 HKEY_LOCAL_MACHINE "Software\Microsoft\NET Framework Setup\NDP\v3.5" "Install"
+  ReadRegStr $dotnet35ver HKEY_LOCAL_MACHINE "Software\Microsoft\NET Framework Setup\NDP\v3.5" "Version"
+  ReadRegStr $dotnet35sp1 HKEY_LOCAL_MACHINE "Software\Microsoft\NET Framework Setup\NDP\v3.5" "SP"
+  StrCpy $7 ${DotNetReqVer}
+
+  System::Call "mscoree::GetCORVersion(w .r0, i ${NSIS_MAX_STRLEN}, *i r2r2) i .r1 ?u"
+  DetailPrint ".NET Framework Version $0 found"
+  ${If} $0 == 0
+        DetailPrint ".NET Framework not found, download is required for program to run."
+    Goto NoDotNET
+  ${EndIf}
+  ${If} $0 == ""
+        DetailPrint ".NET Framework not found, download is required for program to run."
+    Goto NoDotNET
+  ${EndIf}
+
+  ;at this point, $0 has maybe v2.345.678.
+  StrCpy $0 $0 $2 1 ;remove the starting "v", $0 has the installed version num as a string
+  StrCpy $6 $0
+  StrCpy $1 $7 ;$1 has the requested verison num as a string
+
+  ;now let's compare the versions, installed against required <part0>.<part1>.<part2>.
+  ${Do}
+    StrCpy $2 "" ;clear out the installed part
+    StrCpy $3 "" ;clear out the required part
+
+    ${Do}
+      ${If} $0 == "" ;if there are no more characters in the version
+        StrCpy $4 "." ;fake the end of the version string
+      ${Else}
+        StrCpy $4 $0 1 0 ;$4 = character from the installed ver
+        ${If} $4 != "."
+          StrCpy $0 $0 ${NSIS_MAX_STRLEN} 1 ;remove that first character from the remaining
+        ${EndIf}
+      ${EndIf}
+
+      ${If} $1 == ""  ;if there are no more characters in the version
+        StrCpy $5 "." ;fake the end of the version string
+      ${Else}
+        StrCpy $5 $1 1 0 ;$5 = character from the required ver
+        ${If} $5 != "."
+          StrCpy $1 $1 ${NSIS_MAX_STRLEN} 1 ;remove that first character from the remaining
+        ${EndIf}
+      ${EndIf}
+      ${If} $4 == "."
+      ${AndIf} $5 == "."
+        ${ExitDo} ;we're at the end of the part
+      ${EndIf}
+
+      ${If} $4 == "." ;if we're at the end of the current installed part
+        StrCpy $2 "0$2" ;put a zero on the front
+      ${Else} ;we have another character
+        StrCpy $2 "$2$4" ;put the next character on the back
+      ${EndIf}
+      ${If} $5 == "." ;if we're at the end of the current required part
+        StrCpy $3 "0$3" ;put a zero on the front
+      ${Else} ;we have another character
+        StrCpy $3 "$3$5" ;put the next character on the back
+      ${EndIf}
+    ${Loop}
+
+    ${If} $0 != "" ;let's remove the leading period on installed part if it exists
+      StrCpy $0 $0 ${NSIS_MAX_STRLEN} 1
+    ${EndIf}
+    ${If} $1 != "" ;let's remove the leading period on required part if it exists
+      StrCpy $1 $1 ${NSIS_MAX_STRLEN} 1
+    ${EndIf}
+
+    ;$2 has the installed part, $3 has the required part
+    ${If} $2 S< $3
+      IntOp $0 0 - 1 ;$0 = -1, installed less than required
+      ${ExitDo}
+    ${ElseIf} $2 S> $3
+      IntOp $0 0 + 1 ;$0 = 1, installed greater than required
+      ${ExitDo}
+    ${ElseIf} $2 == ""
+    ${AndIf} $3 == ""
+      IntOp $0 0 + 0 ;$0 = 0, the versions are identical
+      ${ExitDo}
+    ${EndIf} ;otherwise we just keep looping through the parts
+  ${Loop}
+  ;check to see if v3 and/or v3.5 is installed
+
+
+  ${If} $0 < 0
+    ${If} $dotnet3 == "1"
+          DetailPrint ".NET Framework Version 3 found"
+          ${If} $dotnet35 == "1"
+                DetailPrint ".NET Framework Version 3.5 found"
+                             ${If} $dotnet35sp1 != "1"
+                                  DetailPrint "SP1 needed. Installing..."
+                                  Goto DownloadDotNET
+                            ${EndIf}
+                DetailPrint ".NET Framework Version 3.5 SP1 found"
+                Goto NewDotNET
+          ${EndIf}
+    ${EndIf}
+    DetailPrint ".NET Framework Version found: $6, but is older than the required version: $7"
+    Goto OldDotNET
+  ${Else}
+    DetailPrint ".NET Framework Version found: $6, equal or newer to required version: $7."
+    Goto NewDotNET
+  ${EndIf}
+
+NoDotNET:
+    goto DownloadDotNET
+OldDotNET:
+    ReadRegStr $DN3Dir HKLM "SOFTWARE\Microsoft\.NETFramework" "InstallRoot"
+    StrCpy $DN3Dir "$DN3Dir\v3.5\csc.exe"
+
+    IfFileExists $DN3Dir NewDotNET
+    goto DownloadDotNET
+
+DownloadDotNET:
+  DetailPrint "Beginning download of latest .NET Framework version."
+  inetc::get /TIMEOUT=30000 ${DOTNET_URL} "$TEMP\dotnetfx35.exe" /END
+  Pop $0
+  DetailPrint "Result: $0"
+  StrCmp $0 "OK" InstallDotNet
+  StrCmp $0 "cancelled" GiveUpDotNET
+  inetc::get /TIMEOUT=30000 /NOPROXY ${DOTNET_URL} "$TEMP\dotnetfx35.exe" /END
+  Pop $0
+  DetailPrint "Result: $0"
+  StrCmp $0 "OK" InstallDotNet
+
+  MessageBox MB_ICONSTOP "Download failed: $0"
+  Abort
+  InstallDotNet:
+  DetailPrint "Completed download."
+  Pop $0
+  ${If} $0 == "cancel"
+    MessageBox MB_YESNO|MB_ICONEXCLAMATION \
+    "Download cancelled.  Continue Installation?" \
+    IDYES NewDotNET IDNO GiveUpDotNET
+  ${EndIf}
+;  TryFailedDownload:
+  DetailPrint "Pausing installation while downloaded .NET Framework installer runs."
+  ExecWait '$TEMP\dotnetfx35.exe /q /norestart /c:"install /q"'
+  DetailPrint "Completed .NET Framework install/update. Removing .NET Framework installer."
+  Delete "$TEMP\dotnetfx35.exe"
+  DetailPrint ".NET Framework installer removed."
+  goto NewDotNet
+
+GiveUpDotNET:
+  Abort "Installation cancelled by user."
+
+NewDotNET:
+  Pop $7
+  Pop $6
+  Pop $5
+  Pop $4
+  Pop $3
+  Pop $2
+  Pop $1
+  Pop $0
+!macroend

MSWindows/mvc.nsi

@@ -44,6 +44,8 @@ Var ZUGO_TERMS
 !include "MUI.nsh"
 !include "FileFunc.nsh"
 !include nsDialogs.nsh
+!include LogicLib.nsh
+!include "DotNET.nsh"
 
 !insertmacro GetParameters
 !insertmacro GetOptions
@@ -219,6 +221,12 @@ FunctionEnd
 ; !insertmacro MUI_PAGE_LICENSE "license.txt"
 
 ; Installation page
+; Not 100% sure but this should be the version that corresponds to 3.5 SP1
+!define DOTNET_VERSION "3.5.30729.01"
+Section "Main Section (Required)"
+  SectionIn RO
+  !insertmacro CheckDotNET ${DOTNET_VERSION}
+SectionEnd
 !insertmacro MUI_PAGE_INSTFILES
 
 ; Finish page