First for all, this not fix anything. Secondly, its the easiest way to work with hammer again! Go and find file ...Steam\steamapps\common\Counter-Strike Source\cstrike\gameinfo.txt Rename file or make backup/copy so you not lose it !!! Download and replace original file with this ...Counter-Strike Source/cstrike/gameinfo.txt [This](https://dl.dropboxusercontent.com/u/38118182/source%20sdk/cstrike/gameinfo.txt "This") Open Source SDK and choose Engine Version: Source Engine MP Current Game: Counter-Strike: Source Then choose Edit Game Configurations Edit... Change Directory Browse... Letter:\Program Files (x86)\Steam\steamapps\common\Counter-Strike Source\cstrike Select Ok Ok Re-check again Engine Version: Source Engine MP Current Game: Counter-Strike: Source Now try launch Hammer Editor. It give you some trouble, Run it anyway... New pop up window, choose Cs:s. If you this point have successfully opened Hammer Editor, close it! Shutdown Source SDK. Open Source SDK and Hammer again Then move in Hammer Tools Options... Tab Game Configurations Game Executable Directory (ex:c:\Half-Life): $SteamDir\steamapps\common\Counter-Strike Source Tab Build Programs Game executable: $SteamDir\steamapps\common\Counter-Strike Source\hl2.exe Place compiled maps in this directory before running the game: $SteamDir\steamapps\common\Counter-Strike Source\cstrike\maps ------------------------ Yes, Hammer will *lag and also crash randomly. And you can't run Cs:s game anymore when you use this wrong gameinfo.txt file!!