Disappointing fps with Asus EAH 4850 1GB

Ok, here's the deal, a little while ago I bought an Asus radeon EAH4850 1GB, to improve my performance in games over my previous card (which was pathetic). I uninstalled the old drivers, ran driver sweeper in safe mode and installed the drivers for this card, it all works ok on desktop but in game my frames are way lower than they should be.

My system configuration is:

Phenom 9500 @default clocks
Asus radeon HD 4850 1GB @default clocks
2GB RAM (unsure of what make or speed, comes out as 5.9 on vista experience rating though, if that's a help)
Windows vista home premium OS

I ran CSS video stress test on all max at 1440x900 max settings and averaged 107fps, pretty pathetic for such a high performance card. A friend got about 280 fps with Gigabyte 512mb, so something is seriously wrong. I don't have any other benchmarks for it right now, will get some later.

Basically, do you have any idea what has caused this?

I don't think it could bottleneck it that much in CSS, it's not the most processor intensive game in the world now is it?

Your ram is in two dimms of 1 GB or just one 2GB dimm? Make them pairs of dimms... And get another 2GB of ram. 2GB ram is the least requirement for vista I think... I don't think your CPU is such a bottleneck. Ram must be in pairs of dimms so it runs in dual channel.

It's the epitome of a CPU instensive game... not literally, but the graphics cards have so far surpassed what is needed in that game that the only thing holding it back is the CPU.

2fast4u, his card is a 4850 as well, that's why I didn't specify a type. Also, I want to be able to get more graphically intensive games so that's why I wanted the boosted performance. About the CPU bottleneck, that seems to be the case, I shall not doubt the Tom's Hardware gurus again. After reading up on it I used the Vista TLB patch disabler and saw my fps in the CSS video stress test go up to 170, and that could surely be boosted further with a little overclocking. So basically thanks for the help, and I'm glad the solution was so simple, I've seen no end of threads on other forums where an answer was never reached.