ATI Radeon HD2600 XT with Bioshock, Alien vs. Predator 2, SpellForce

Hello

can someone help me here!
I have the following problem: When I Play with Nvidia logo would like to play then I have problems with it either plunge them in some cases even gives up the blue screen or have any graphic errors. I actually always use the latest graphics drivers have already updated all firmwares and others from the board. Write s still some problems with this title: Battlefield 2 (2142 no probs), Bioshock, Alien vs. Predator 2, SpellForce ...

Thanks in advance!

My System
AMD Athlon (tm) 64 X2 Dual Core
2GB DDR2 800
Asus M2A-VM HDMI
ATI Radeon HD2600 XT
Win XP SP3

Problems with which games?
Which PSU?
Test ram with Memtest.
see if motherboard is dusty.

PSU: BQT E5-450W
Memtest: done
Everything had completely dismantled the computer cables, plugs and sockets are all ok as far as I could see.
3DMark06 gave CPU Core0 66 ° C and Core1 to 70 ° C in empty so at 50-54 ° C GPU 69 ° C in operation and empty 50-52 ° C do not know if this is important and do not know what temps are critical for ....

Hi,

Both the ATI Radeon HD 2600 XT and eVGA GeForce 8600 GT didn't have enough muscle to be playable, but the new ATI Radeon HD 3850 is playable at 1600x1200 with medium quality settings.