280 GTX Help

Hi there everyone ;

I have a problem with my graphic card but its a software problem i think. I tested it in several games and i have a problem and i'm not happy with it.

I tested it in ;

Team Fortess 2
Left 4 Dead
Half-Life 2
Crysis Warhead
Need For Speed Undercover


I know first 3 are steam powered games. I got 40-60 fps in these games and its hard to play in that games with that frames and in last 2 games i got low fps again but bad shadow quality too.

What should i do ?

My system :

Asus Rampage Formula Motherboard
Intel q9300 Quadcore with Thermaltake Cooler
4x1gb 1033mhz OCZ Ram
2x500gb Samsung HDD
ZOTAC Geforce 280 GTX
LCPOWER 1000watt Power Supply

And i use Windows XP 64-bit and latest driver of Nvidia 200 series.

edited , sorry about that. (:

1680x1050 resolution , not full details in that games. I tried it in Vista 64-bit and it's same. I think you are right about my OS. I'll try it 1-2 days later after another solutions. (:

Thanks.

Thanks both coozie7 and werxen. I'll try driversweeper and then check the hardware and psu cables. If it's not work i'll format and install 32-bit.