windows x64 setup

build/win32/code.iss

@@ -30,6 +30,8 @@ SourceDir={#SourceDir}
 AppVersion={#Version}
 VersionInfoVersion={#RawVersion}
 ShowLanguageDialog=auto
+ArchitecturesAllowed={#ArchitecturesAllowed}
+ArchitecturesInstallIn64BitMode={#ArchitecturesInstallIn64BitMode}
 
 [Languages]
 Name: "english"; MessagesFile: "compiler:Default.isl,{#RepoDir}\build\win32\i18n\messages.en.isl" {#LocalizedLanguageFile}
@@ -790,6 +792,28 @@ Root: HKCU; Subkey: "SOFTWARE\Classes\Drive\shell\{#RegValueName}"; ValueType: e
 Root: HKCU; Subkey: "SOFTWARE\Classes\Drive\shell\{#RegValueName}\command"; ValueType: expandsz; ValueName: ""; ValueData: """{app}\{#ExeBasename}.exe"" ""%V"""; Tasks: addcontextmenufolders
 
 [Code]
+// Don't allow installing conflicting architectures
+function InitializeSetup(): Boolean;
+var
+  RegKey: String;
+  AltArch: String;
+begin
+  Result := True;
+  RegKey := 'SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\' + copy('{#IncompatibleAppId}', 2, 38) + '_is1';
+
+  if '{#Arch}' = 'ia32' then begin
+    Result := not RegKeyExists(HKLM64, RegKey);
+    AltArch := 'x64';
+  end else begin
+    Result := not RegKeyExists(HKLM32, RegKey);
+    AltArch := 'ia32';
+  end;
+
+  if not Result then begin
+    MsgBox('Please uninstall "{#NameShort}" ' + AltArch + ' before installing this package.', mbInformation, MB_OK);
+  end;
+end;
+
 function WizardNotSilent(): Boolean;
 begin
   Result := not WizardSilent();