I figured out the cause of my BSOD's under Vista (which are not the win32k BSOD everyone else was getting) -> latest Intel Chipset Drivers After fresh install of Vista I installed the Intel Chipset drivers and force updated drivers that didn't install on their own since they were newer than Microsoft drivers. Apparently, Intel's driver for "975x Memory Controller Hub - 277C" doesn't agree with the ATI drivers (or vice versa). Reverting back to the Microsoft driver no longer BSODs when I enable and disable Crossfire. Haven't tried gaming yet, but will do that in a sec. EDIT: Nevermind, after 2 more restarts I got stuck with the BSODs again....argh EDIT2: Reinstalled Vista, but this time I didn't install the Intel chipset drivers and installed 7.3 Cats. I got the win32k BSOD at reboot, but was easily corrected with the ATIStart.bat. Crossfire worked without further BSODs (yay!) So for me it's definitely the chipset drivers. I'm going to try Windows XP (which also got errors) without the chipset drivers and see what happens.