I just installed Vista Ultimate 64 in the Boot Camp generated partition of a 8-core Mac Pro 3.2GHz. Then I pulled the Radeon HD 2600 XT out and replaced it with a PC compatible BFG nVidia GeForce 8800 GTX (768MB - overclocked) --- which, by the way, requires two power feeds. Thankfully I had two proprietary power cords from Apple and the motherboard has two 6 pin power feeds. The GeForce 8800 GTX booted up just fine with Vista as the default boot volume. I've installed the latest driver from nVidia. It's running at 2560x1600 on the 30" Cinema. Next I'm going to run some gaming benchmarks and report back. Moo ha ha.