I just built a new system with a 4870x2 running Vista 32 and my FPS was worse then my 7950GT and I could only get 1400 by 1050 on my desktop (Samsung Syncmaster 244T) and WoW where as I got 1900x1200 on my old card. To say the least I was highly disappointed, I tried various things as you did too including updating to 8.8 drivers but still no luck. On a single WoW instance I get 25-30 FPS tops and with 5 instances running I lag in SW. I'm running the following main components on a newly built rig:

Core 2 Quad Q6600 w/ 4GB RAM only 3GB showing until I upgrade to 64bit on a BIOSTAR TPower I45 LGA 775 MB

I messed around with it for 3-4 days and still have the card and am thinking about returning it...the card runs Crysis great but I mainly bought this when I got back into WOW/MB + RAF.

I would like to keep the card but it would seem that I'm better off with a 260ftw or 280 and also have some money left over. Sorry I wish I could give you better news/hope with my experience, I could be doing something wrong I just don't know what else to try at this point.

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Just saw some responses to this post so, I'm also running a Antec TruePower TPQ-1000w