Thanks for the help, everyone! Every suggestion helped a little.
Poornaprakash, your suggestion to move the pagefile from the C: drive to my D: drive was the biggest help, though. I followed the steps below and it cleaned up over 20 GBs off my C drive!http://mintywhite.com/vista/vmaintenance/performance-boost-move-page-file-to-another-physical-drive/
Seriously, thanks again, everyone. You were a big help.
If anyone else asks, Windows 7 Professional, SP 1, with all Windows Updates as of 08/14/2011 installed and CCleaner and Google Chrome (both of which don't like to be installed to any drive other than your C: Drive) should take up almost exactly 30 GBs.