First of all here are my computer specs

AMD Athlon 64 processor
1 gig of RAM
Radeon x1600 video card
Asus K8V-X SE mobo
SoundMAX Integrated Digital Audio
running Windows Vista Ultimate

So after installing and getting all my drivers set up I figured I'd try out some games to see how they played. Well, most games are working fine, but neither Half Life 2 or Counterstrike Source have sound, and I really have no idea why. Sound works outside of those games, and it works fine for other games, so I don't know what the problem is. I also haven't been able to find anyone else who is having this problem, so any insight would really be appreciated.