Aside from audio drivers (which have to be checked), which PSU are you running? The "crappy" 500W or the "old" 420W? I'm asking since I have the same P4 541 and it's power-hungry... like you would not believe.
Also, I had problems with sound dying too when my 541 was once overclocked too high. Is yours oc'ed too?
Have you run Memtest86+ to check the Ram?
Could it be that your GPU is overheating, creating lags in your games? Or asking too much from that 7600GT? It's a (relatively) old card - an old generation for those newer games.
John