6600GT in game problem

[lstic]

First of all i apologize if there's already been a thread like this..
Yesterday i took Gainward 6600GT Golden Sample and installed it. When i run games some strange things appear on screen like stripes, geometric shapes, sometimes transparent and invisible textures... The temp in desktop working mode id about 70-75 C degrees and after playing max 85...it's high but i doubt that it's a problem... I think that the real problem is that my power supply is slightly under 200W of power (lol) and it gives 9A on each power connector..
I just want to know if that is a real problem and not something else before i buy a new supply...
I tried different versions of forceware, overclocking, underclocking but all the same, maybe sometimes a small difference.
Thanks

[lstic]

---bump---
Just installed Win XP, i have dual boot, on XP it runs without any problem, on vista always the same...
Any advices?