Sound Issue

I've asked this question 5 months ago when it began, and it still hasn't been fixed yet.

I recently switched to Windows 7 Ultimate x64 from XP, and suddenly the sound of footsteps and gunfire has disappeared from my headset. I can still hear voices and stuff fine, but it's getting really hard to play with real players when you can't hear where they are. I already tried going into msconfig and disabling the useless stuff, also tried reinstalling like 5 times. My crossfire sound is turned up, and so is my system sound.

Anyone else have any more ideas?