Well, as I said I was afraid of earlier, it does sound like you have a video card on the way out.
1. I know your sound is OK, but please just turn it off, and see if that affects game performance.
2. Try normal resolution for your game but set the colours to 24bit then 16 bit and see if that makes any difference?
3. In your control panel, display, troubleshooter, try setting "hardware acceleration" to 50% then lower until off.
I would guess that "event viewer" doesn't show anything in the logs?
:(
