I Buy a XFX Geforce GTX 260 / 768 MB.
before buy it, i have a MB ECS P33T-A (PCI-Express 1.0)
i install GTX 260 on it and play game.
but for increase performance, i change MB and buy ECS P43T-A2 (PCI Express 2.0)
but my game performane doesn't change!
i play crysis in 35 FPS (1680*1050 and 2x anti-aliasing) and now play just in 37 frame!
i hoped play in 45 frame and better!
why pci express 2.0 affect week?
Sorry to say this but your money was not well spent.
The GTX260 is not fast enough to need a PCI-E 2.0 motherboard. A full X16 PCI-E 1.0 or 1.1 slot is enough.
All I can suggest is either overclocking your CPU, replacing it with a faster CPU or turning AA off.