I assume you refer to your graphics card when you say 8800? Nvidia GeForce 8800? The game should work beautifully on that, so this is an interesting concern. However. Sound cards are in fact an issue. By some act of All-Father, I can play it with an onboard, but many people cannot. Furthermore, just like a graphics card's drivers, sound card drivers are a huge issue. I suggest you try disabling your sound or updating your drivers and seeing if that's where the problem lies. If that doesn't work, could you test your rig out in Single Player? I'd like to know the results, as I've had no problem with a 9600.
Oh, also, I know this is a bit repetitive but it helps with some cases.
Start->Run->dxdiag
Check what your computer is listing as your graphics card and sound card. It may have the wrong idea.