How to get Windows Version 

procedure TForm1.WinVersion;
Var
 OSVer : TOSVersionInfo;
begin
 OSVer.dwOSVersionInfoSize := SizeOf(OSVer);
 GetVersionEx(OSVer);
 If OSVer.dwPlatformID = VER_PLATFORM_WIN32_WINDOWS Then
  Edit1.Text := Format('Microsoft Windows 95 ver %d.%d (Build %d)',
                [OSVer.dwMajorVersion,
                 OSVer.dwMinorVersion,
                 OSVer.dwBuildNumber AND $FFFF]);
// Check for Microsoft Plus!
If SystemParametersInfo(SPI_GetWindowsExtension, 1, Nil, 0) Then
 ShowMessage('PLUS! Installed');
end;