XFX 4890, Win7, 60*c, 3 version of drivers

Hi,
Want an opinion on what you guys think is wrong with my 4890.
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Backstory: The first install I did with this card produced some shitty results within games; the directx9 games seemed to perform at about par with some benchmarks but the dx10 games where very lack luster (about 8800GT speeds). I produced a 13960 in 3dM06 with a Ph2 x4 955 @ 3.3GHz and the 4890 oc'ed to 900/1000. It seemed temperamental as it produced a 14900 once - GTA 4 would lock-up briefly with a black screen and then resume the more I overclocked it (no artifacts) - when it did lock up (with a mild oc), it would turn out with white and sometimes blue stripes up and down on the screen. Sometimes different colors.
P.O.ed, I then d/led a 3rd party tweaker; noticing the clock speed was sitting @ 250 (power saving speed), I bumped it up to 850 (thinking it was the tweaker misreading the speed; locked up fully, fan running @ full speed to a auto restart.
I then figured I'd d/l Driver Cleaner to help out with Driver Sweeper. As soon as I cleaned the drivers with DC, I ended up with 2d and 3d arifacts - yet the card was running @ full steam now and my scores took a jump from hell. Did I f--- the card up or was it f---ed to begin with? Your op.
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Going from a 8800GT, uninstalling drivers, using Driver Sweeper and Driver Cleaner in safe mode, using 2 different catalysts/driver sets @ stock speeds I get 2d artifacts as soon as I enter windows. Obviously it artifacts within games also - my heat is not an issue as the card sets at 48*C idle and around 60 - 65*C load.

Is the memory on this thing shot? Or has the transition from nV to ATi caught this card up? I kept Rivatuner running from the uninstall of the 8800GT also; could Riva be the cause?

Thanks for reading this novel.

I am running a XFX HD4890 XT myself and have had no issues but nvidia drivers will screw you up and these cards need a very strong powersupply to work right.. patch all your DX 9 and 10 up from microsoft and if that doesn't work then do a fresh install of windows.. your OS is really not fully surported yet BTW..

Corsair TX750w 60a on 1 12v rail, Asus M4A78T-E
All Win7 updates are current.

Wondering if Riva may be at fault where-as I installed the Riva when I had the 88GT. Maybe Riva is enforcing some profiles from having the 88GT installed?