I had a similar problem to most people - poor graphical performance fixed up by the /nosound trick.
Did a dxdiag and saw that I had 8 "sound" tabs. Set the hardware acceleration on each of them to "none" except the first one (the real one, I assume). This did result in a performance boost.
I have no idea why there were suddenly 8 sound tabs, but this seemed to be the root of my problems.
