HL2 and EP1 npcs dont make sound.

I have just set up a dedicated server on my other computer, and have installed it correctly. I think.

Upon playing on it, my friends and I couldn’t hear any npcs making noise except for the Hunter. I have found (in unanswered threads) that there is a file located somewhere within one of the GCF files that could correct the problem. Any ideas where this file is/on how to fix this?

I guess not.