Attention people with actual computer knowledge, can you help me with my computer performance issue?

I'm running an Alienware Aurora 7500 (specs at the bottom) and I'm not stupid when it comes to computers, but I am stumped. When I first got my computer, it worked for a week or two, but then COD4 and GH3 stopped running well, because computer usage went up to 100%, with only Xfire running in the background. I did have Xfire before the issues, so it's not the problem. How can I get my computer to perform at its fullest again?

Foxconn nForce 590 SLI, AMD Athlon 64 X2 5200+ 2.6GHZ 2MB L2 Cache, 3GB DDR2-800 RAM, 250GB Hard Drive, Nvidia GeForce 8800GT 512MB

Attention people with actual computer knowledge, can you help me with my computer performance issue?live update

a computer like that should run those games fine, have you tried running a virus scan?

or defragmenting?

Attention people with actual computer knowledge, can you help me with my computer performance issue?norten

Have you tried updating all the drivers to the latest? Perhaps it's a driver conflict or something.

A possible solution if all else fails is just re-imaging the entire machine, but that's a pain in the butt, especially if you have a whole bunch of stuff you need to backup first.

Another thing is: try resetting the BIOS back to what the factory settings were, but this only applies if you tried overclocking.
Please follow these links: Free AVG software, in my opinion one of the best anti virus out there. http://www.download.com/AVG-Anti-Virus-F...

Next, download free spywareblaster here: http://www.download.com/SpywareBlaster/3...

Next: Advanced Windows Care V2 Personal

http://www.download.com/Advanced-Windows...

These 3 freebies are all i've used now for about a year. They keep me running faster than ever... Hope this helps!!
i would dump symantech, as they are bad, and go with Avast anti-virus, since thats the best currently, and i would try doing a disk check along with deframentation, and anti-spyware scan with spybot.