In an earlier thread I asked what upgrades were needed to run World of Warcraft on maximum settings at 60 frames per second, however, after speaking to a few friends with similar systems who do run it at 60fps maxed out, I wanted to know why my PC would not. My specs are:
Your problem is the GPU and power supply. The PSU sucks, and the GPU is not really meant as a gaming card. What you want to do is get something like a 6850 or GTX 460 AT LEAST for 1080p. After that, you shouldn't have any big issues.
remember your friends may be playing at monitors with lower resolution.
as striker said, your gpu is definitely your bottleneck. however, you can get much more playable performance if you would just lower the anti-aliasing. 8x anti-aliasing is really unnecessary at your high resolution, and will only serve to kill your frame rates while providing a negligible improvement in image quality.
also a 5670 while the weakest component in your computer, can provide respectable performance at 1080p in most games as long as you are willing to make minor compromises such as lowering AA or playing at 30 fps instead of 60. If graphics or framerates are of high importance to you, then you can certainly upgrade to something like a 6850. Im not so sure about the quality of your power supply though.
Yea like all of the previous comments, your GPU is pretty terrible. It's not terribly old, but it is just a lower end card. gtx 460 is a solid choice, I'd go 560 if you want to future proof yourself a bit more, and i'd get at least a 750 watt psu