One utility I do like is called WinDirStat.
http://windirstat.sourceforge.net/
This utility provides you with a graphical representation of all the data on your drive. You can easily identify what directories are HOG the space on your Disk.
You don't need to install windirstat utility to run it . . . just uncompress the files into a directory and click on the windirstat executable.
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Also since I'm on this subject . . . .
http://osswin.sourceforge.net/ is an excellent resource for opensource windows software.