This is tangential, but do a search for *.tmp [for temporary files].
Deleting unused tmp files is good in a variety of ways, and you may find some large files along the way.
Couple of other suggestions:
<1> Check your download directory, and throw away downloads you no longer need; if you have large installers there you may be suprised how much space this saves you.
<2> Go through your installed software (Add/Remove Programs), and uninstall software that you no longer use.
Curious to see how much space you gain back.
