[defcon1_es]

Ampliado para windows vista:

Código Delphi [-]
function TForm1.GetOSVersion:String;
var
  OSVersion: TOSVersionInfo;
  FVersion,FPlatform,serPack:String;
  FPlatformID: DWord;
begin
   OSVersion.dwOSVersionInfoSize := SizeOf(OSVersion);

   if GetVersionEx(OSVersion) then
      begin
         FVersion := Format('%d.%d (%d.%s)',[OSVersion.dwMajorVersion, OSVersion.dwMinorVersion,(OSVersion.dwBuildNumber and $FFFF), OSVersion.szCSDVersion]);
         FPlatformID:= OSVersion.dwPlatformID;
         case OSVersion.dwPlatformID of
             1:begin
                Case OSVersion.dwMinorVersion  of
                0: FPlatform := 'Windows 95';
                10: FPlatform := 'Windows 98';
                90: FPlatform := 'Windows Millennium';
                end;
               end;
             2:begin
                Case OSVersion.dwMajorVersion  of
                3:FPlatform := 'Windows NT 3.51';
                4:FPlatform := 'Windows NT 4.0';
                5:begin
                     if OSVersion.dwMinorVersion=0 then
                        FPlatform := 'Windows 2000'
                     else
                        FPlatform := 'Windows XP';
                  end;
                 6:FPlatform := 'Windows Vista';
                 end;
               end;
            else
                FPlatform := '';
         end;  //of case
      end; //of if
      serPack:=OSVersion.szCSDVersion;
   result:=FPlatform+' '+serPack;
end;

//y para llamar 

Label3.Caption := GetOSVersion;