It could be your internet connection. If you're running a 56k in some online games your FPS could take a hit. In these circumstances, no amount of hardware can make up for it. What kind of latency are you getting? Make sure to stop torrents and what-not as uploading hits your bandwidth quite hard.
Also, open Task manager and visit the CPU tab make sure there is no process called "System Interrupts" popping up above 5% of CPU load. That's caused by bad drivers somewhere and your CPU having to pull double duty to make up for them.
Last edited by NinkobEi; Jan 22, 2013 at 04:56 PM.