This is a pretty light load.  That hints that something else is the
bottleneck.  Have a look in the taskmon at CPU usage and page swaps

There could still be a fair bit of hidden i/o going on.  What does it
sound like when you put your ear to the case?  Can you hear a lot of
clicking.  You might get a copy of O&O defrag evaluation and tell it
to sort all your files physically on disk by last access date.  Also
tell it to do the various auxiliary defrags, including directories and
registry. Do a pruning of junk in your directories first. You might
use the Ace utilities  evaluation pruner for that to prune both the
registry and files.  Perhaps you have a directory clogged with useless
unused files.

Windows tends to fill up over time with undeleted temp files.

see http://mindprod.com/jgloss/defragger.html
see http://mindprod.com/jgloss/registryfixer.html