Um, have you checked your swap space? That sounds like it is attempting to swap to disk.
Most systems should have their swap set to the maximum that windows suggests (usually 2-2.5x ram.) Also it's a good idea to try to have it allocate it as one huge chunk, rather than microsoft's silly "allocate disk when I need it" strategy.
It is most noticable on a system with slow disks, but you'd see it on any system where the swap is heavily used (do you use firefox? update it to the latest version, the older versions tended to hog huge amounts of virtual ram and page out a lot.)
To check, I believe in win7 you can still get to the performance tab using my computer->right click->properties->advanced. If not, you have to poke around in the advanced settings of the control panel to figure out where it is. There should be a setting for virutal memory under performance -> advanced, in there you can set the paging file to the maximum recommended or allow it to coast between a minimum (should be your memory size) and the maximum (up to 2X memory.)
If that isn't it... drivers really is the only other issues you can have in windows that would cause problems -- other than actual hardware issues (check your system log to make sure you aren't getting any disk/bad sector errors, in which case do a diskcheck with sector recovery.)
Hope that's helpful.