I dunno, but maybe this will help, I've had this problem before. I install a mod for halflife be it CS, DoD, FLF whatever, I install it to say c:sierrahalflifeDoD
but when it installs it installs under this..
c:sierrahalflifeDoDDoD try looking in the folder and seeing if this is the case, if so move the folder containing the game into the Halflife folder and your problem is solved.. if that doesnt help then I have no idea hehe
