It will scan the drive and give you a breakdown of every single folder on the drive and the size of the folder and files. Once installed and opened you need to select only the C drive and do a scan. Just search it on Google (I am not sure if I can post links on here). These are only possibilities but to really find out what folders are taking up the space download and install a program called Windirstat. Also, any picture applications (such as Picasa) store their picture libraries in a user's personal folders. Even with ITunes, do you purchase videos at all?- this will also take up space in your personal folders. Also, your ITunes library is stored in your Music folder so if your music collection is huge then your folder will be also. Do you listen to audio discs in Windows Media player (WMP)? If so, WMP may be set to rip every audio disc that you play. The System Restore is stored in a hidden folder directory on the C drive. If most of the data is in the folder of your profile (My Documents, Music, etc) then it will most likely not be System Restore or any other Windows related feature/application.

C drive full windows 7 solution