It wasn't pretty. I don't yet have that hard-to-find molex adapter to power the 8800GTS card yet (local dealer and Apple Canada didn't know what I was talking about). As a temp fix, I ran the 6-pin power chord from my PC's guts (been building my own for about 15 years) into the guts of my Mac and attached to to the 8800GTS. (see the attached pic). I installed the driver for WinXP and wham! it soared to a respectable 9826 on 3dMark. My Mac's spec when running Windows under BootCamp is: mac pro 2.66 GHz Quad Core Zeon (2X Dual core 64 bit w/1333MHZ front side bus) 3GB Ram Single 250GB Western Digital Caviar 8mb cache Windows XP SP2 (32 bit) w/Direct X 9.0c the GeForce 8800GTS 640MB with latest driver for XP Found this 5.25 inch power supply on the web, which I might consider using in lieu of powering it from the board....reason is I want to still run my 7300GT for a 3 monitor set up and Mac Pro's guide says don't draw more than 300W total for PCI-e cards....the GeForce 8800 GTS alone takes 24A peak at 12V. So then I put the card back into my PC and ran it on 3dMark which I hadn't done yet. Here are my comparable PC specs: Asus M2N-E mobo AMD Athlon 64 Dual Core 4200+ CPU 4GB Ram (effectively 3.5GB only under 32 bit Vista) Two 160GB 16mb cache Seagate Barracudas in Raid 0 Windows Vista Ultimate (32 bit)w/DirectX 10 the GeForce 8800GTS 640MB with latest driver for Vista It scored 7030. The greatest lesson I learned? Apple is completely unprepared for the wave of "PC Enthusiasts" about to invade their shores with all kinds of demands for weird parts for modding and customizing. I think they're seeing the past with a market of folks who buys Macs precisely because they don't homebrew-and are frustrated trying get Windows to work-and to the future at technology that won't need (or allow?) any homebrewing anymore (so they think;-). Which leaves us mod-happy PC converts in the middle somehere risking our Pro's to try wierd things to make it go faster. But I'm proud and impressed with what I could do with my Pro tonight and glad to be back. ps the following picture will seem odd and even offensive to some old-time Mac users and downright sexy to PC enthusiasts. In the background is my 3dMark score.