wloadwadfile

My friend is having a problem playing ESF on his computer... he has both Half-Life 1 along with Counter-Strike and Condition-Zero. Does Condition-Zero effect anything? But anyways everytime he tries to play, he gets an error that says 'W_LoadWadFile: couldn't load gfx.wad'. Any help? :S...

Dear..... When i want to create a lan game where i can play or fun or train with bots.. i select a normal map from the list and when i click on done.. It crashes and gives me this Error : w_loadwadfile : couldn't load gfx.wad I'm a newbie so don't know what to do? but am i missing something...