If you are trying to find out what’s eating up your precious hard disk space in Windows XP/Vista, WinDirStat is your weapon of choice. A much helpful tool than the brain dead Explorer, WinDirStat analyzes the usage statistics of your hard drive/partition/directory and outputs(along with other data) a treemap, which is a visual representation of how blocks of data are organized on the disk.
Clicking on a block shows you the file/directory physically taking up the space in the directory list(shown in the picture). Comes quite in handy. I just cleaned 1 Gigabytes worth of data cached by Safari 4. If it wasn’t for WinDirStat, I would’ve never known that Safari thinks your hard drive space is infinte! Who knows, may be Steve’s is really is?