I recently visited a friend of mine who had a huge problem with his computer. His main hard drive was filling with data rapidly although he only had the operating system and some applications installed. It turned out that System Restore was using more than 12 Gigabytes of space on this drive alone.
System Restore might be a good way to give users fallback and restore options in case something goes wrong, but the amount of data used is more often than not way out of proportion.
You can check your System Restore settings by opening the Control Panel, selecting System from the links in there and the tab System Restore in the new window.
Update: In never versions of Windows, you need to click on System and Security > System > Advanced System Settings and there on the System Protection tab. You may also load the interface directly from the command line or run prompt by loading rstrui.exe directly.
System Restore can either be deactivated for all drives, activated for some drives or for all drives. If it is activated the settings button will display information about the maximum amount of space which is 12% of the space on the hard drive by default (it may be less on newer versions of Windows but it pays to check the value and adjust it it if appears to be too high).
You can find out about the space that System Restore is currently occupying by using Windows Explorer. Right-click on the System Volume Information folder and select Properties from the menu.
If you feel that the file size of the restore points is too high you can decrease the amount Windows uses in the System Restore menu in the Control Panel. Or, you could do the bold and turn of System Restore on all drives. I have it turned off since the beginning and I never had a problem.
To just get rid of all System Restore points is also easy. Turn off System Restore and turn it back on again afterwards. This cleans all System Restore points that are currently on the hard drive.
Are you using System Restore or do you prefer another method of backing up your files ?