New SP2 install restarts comupter (D3D?)

After the fiasco with spyware this weekend, I wiped my drive and reinstalled XP. This time I decided to install SP2 as well, figuring if it's going to screw anything up it might as well be while the OS is still fresh.

The main problem I'm seeing now is that several games (Tribes 3, Sims 2) are crashing as soon as they get past their menus and into the "3D" parts of the games. I can start them up, go to the options screens and all that... Tribes 3 restarts my computer (as in the whole thing reboots, not just crashes to Windows) as soon as I get into a map. Sims 2 restarts the system after I've loaded a house and it starts getting to the 3D part of the game. My guess is that it's something with Direct3D, as I tried running Tribes 1 and 2 as well (both using OpenGL and they ran wonderfully, no restarting the computer.

Apart from installing SP2, the only other differences are that I installed the newest Nvidia drivers (I think I was one or two iterations behind before I reinstalled Windows). I've double-checked DirectX and it's at the most recent, 9.0c or whatever it is now.

I'm at a loss as to what steps I can take now... Any ideas? It has to be one of those things since everything was working great before the install, and like I said the only things I can think of that are different are SP2 and the new Nvidia drivers.

(EDIT-) Meh.... I don't think I'm much better off with SP2 anyway, so I'm going to go ahead and uninstall it for now and see if that makes things better.

m19