If you're experiencing problems with the Hammer game configuration or SDK Launcher game configuration not behaving correctly, you can follow this procedure to reset the game configurations to the default state.
If after resetting the Game Configuration the tools still do not run correctly, this usually means that the SDK tools cannot find the Gameinfo.txt for the game or mod you want to work with. To fix this error with a Valve Software game (e.g. Half-Life 2, Counter-Strike: Source, etc.), simply run the game then restart the Source SDK. If it is a third-party or custom modification, you will need to manually create a configuration specific to that Mod.