As you can see I had download the Source SDK SP3 . There is somethings that's very confusing . This Source SDK can run the HL2 but it can't run the CS Source when I select Counter Strike-Source and use the Hammer Editor this Source SDK warns me that : The Configuration Information for the game you're trying to edit is invalid or missing ??? Can you guys help me a little about this ? Thank you very much And Sorry about my bad English .