Horrible FPS in WoW..

I've been playing WoW on this system for a year or more..

ASUS P5S800-VM motherboard with latest BIOS
Celeron D 2.53Ghz processor (overclocked it to 2.66Ghz)
1GB PC3200 DDR
BFG GeForce 6800 GT OC 256MB (running latest Nvidia driver)
Twin 80GB hard drives Hitachi 7200RPM (recently ran a defrag)

I used to run 1024x768 with some settings on and the game ran fine. Now I'm running 800x600 with ALL options turned down or off and I'm getting 1.5-3.5 FPS! Most of the time I get 7-15fps, but a lot of times it'll hover around 1.5-3.5fps. Today I dropped below 1fps in Alterac Valley. This never used to happen.

I have the 15% increase in my ghost wolf speed and I press the up arrow key to move and guys with the regular ghost wolf are going faster than me because of my fps lag. It's so bad I can't see a lot of the times.. I just blindly click people and hope they need healing and hope I can get them in time. A lot of times I'll get killed and not have seen why. I just end up dead.

Anyone have any suggestions on what could be wrong?! Could the later patches have affected things so much that they are FPS hungry?! I don't think my system should get this low of FPS.

I'm no expert, but in my 10+ years of gaming experience, I find that game performance tends to suffer when my HDDs get too full. 160 GB goes quick, especially if you do more than just game.

I also have found that WoW plays alot better with 2GB of RAM. Hope that helps some.