Amd Setup / Aion low fps

Hello all, it has been awhile since I have posted, it's good to drop on in again. Anyways my question revolves around the new Video game Aion and my current rig setup.

First with the question... When I play the game itself on High settings, 1280-2024 AAx2 I see reasonably fps when alone in outdoor zones, but as soon as 1 player comes on board it starts to plummit on fps... This is especially the case in towns. My question to you is anything from my system bottlenecking my gameplay.
Here is the rig, it's about 1 year old:

Amd 9500 Phenom Quad Core
Ati Radeon 4850
Ocz 650w PSU
4 Gigs Ram
250G Hd
17" Sharp monitor
Mobo - MCS MCP61PM-GM
win vista 32 home

My GPU does run hot, and I have to crank up the fan to about 75% for it to be around low 70ish degrees, besides that can anything else be slowing me down? Would switching to xp help? Perhaps a faster cpu?

My friend runs a less expensive rig with Win Xp a 24" monitor, all maxed graphics and a 9600gt and he runs it smoothe, something must be the issue.

Thanks for your time guys, and like always, awaiting some good feedback

Yeah that's exactly what I thought... this system should handle the game better than it is.. and my net is fine.. I'm using Rogers High-Speed Cable(Canadian)
Anyways I have class now, I'll check up on the thread in some time, thanks for the quick reply