"If you have lots of data, *that* can be moved to D. "
No, I try to keep data off of C:
"When's the last time you cleaned out all the temp files, downloaded files, cookies and cached web pages?"
I run CCleaner almost daily.
"Are C and D on the same drive? If so and you are confident of your maintenance skills, you can use something like gparted to shrink the D partition and move it away from C, then add the new space to C and give yourself more room. "
Yes they are the same drive, and I thought of using a repartioning program, but would rather do that as a last resort. I've used them before with mixed results.
"There are a few solutions, but I need a little detail about your system. XP or Vista?"
XP
C: and D: are a Maxtor 200G drive that is an upgrade from the stock drive. I also have another Maxtor 200G as an E: drive. I wanted to have my C: as small as possible, basically as home to the OS. It is currently 38G. When I install software, I always install to D: if the install program gives me the option, but often they don't. Running software from Program Files on D: seems to work just as well as from on C:. I wanted D: to to be larger for storage of photos (lot's of hi-res, big files) and music, and E: was to be for video. C: has just gotten polluted over the last couple years by certain software. I basically want to get the drive under 85% so my Diskkeeper software has the breathing room it needs to defrag and optimize the drive.