My old graphics card, a Radeon 5870, died so I decided to go ahead and upgrade and I got a GeForce 670. Now I'm getting blue screens after 5 minutes.
My first intuition was that the problem was having Catalyst drivers and an Nvidia card (I hadn't had a chance to remove Catalyst drivers yet), but I was never able to get through the uninstallation process without blue screening. The computer is stable in safe mode, and I was able to install Nvidia drivers, but I couldn't uninstall Catalyst drivers from safe mode ("Windows Installation Service is not running"). Using driver sweeper I was able to get rid of most of the ATI files, but Catalyst was still listed in the programs, and I was still getting blue screens. I then found a way to get Windows Installation Service working in safe mode, but now the Catalyst uninstaller had been removed by driver sweeper, so I couldn't run that (I took the opportunity to remove all the Nvidia drivers though). I restored the back ups from driver sweeper and also used system restore to go back a few months (when my Radeon card was working fine), but now Catalyst was giving me an error about not finding detection drivers. I then ran the manual uninstallation from the command line, which removed the files from "Program Files", but I still have files in "C:\AMD" and "C:\ATI". It's not clear to me if the Catalyst drivers are still installed or not, device manager says it's using generic VGA drivers, but Catalyst Install Manager is still listed under programs and Catalyst Control Center still runs on bootup, giving me an error message about not being supported by the current drivers (if I manually run it in safe mode, I get a different message saying "No ATI graphics drivers installed"). But this may have all been a wild goose chase, I'm not sure.
Somewhere in all this I also ran Memtest over night, it ran for about 8 hours, 5 complete passes, no errors, and I also swapped the PCIe slot for the GeForce 670 (to no effect).
So after all that, here is the current state of my system:
-Blue screens after about 5 minutes (STOP code is 0x50: PAGE_FAULT_IN_NONPAGED_AREA, which is why I ran Memtest)
-Stable in safe mode (this makes me think it's not a hardware issue).
-Catalyst is installed, but no drivers?
-No Nvidia drivers.
Specs (everything stock):
Intel Core i7-860
2x2GB G.SKILL Ripjaws Series DDR3 SDRAM DDR3 1600
MSI P55-GD65 LGA 1156 Intel P55 ATX
CORSAIR CMPSU-750TX 750W ATX12V
XFX HD-587X-ZNFC Radeon HD 5870 (old) / GIGABYTE GV-N670OC-2GD GeForce GTX 670 (new)