If you’re running low on space and your favorite maintenance tool isn’t helping, you may find that iTunes is hogging a few gigs of your system in C:\Documents and Settings\All Users\Application Data\Apple Computer\iTunes (or ~/Library/iTunes on a Mac). Just head in there, delete the backup folders, and watch your hard drive free up tons of space. If you are using Vista or Windows 7 the location is C:\Users\User Name\AppData\Roaming\Apple Computer\MobileSync
