thanks to http://www.ghacks.net/2012/10/05/manage-system-restore-from-the-command-line/
- vssadmin list shadows – This command lists all existing shadow copies on the system
- vssadmin delete shadows /for=c: /oldest – This command deletes the oldest shadow copy on drive C
- vssadmin delete shadows /for=d: /all – This command deletes all existing shadow copies on drive D
- vssadmin delete shadows /for=c: /shadow=ID – Deletes the selected shadow copy. The IDs are listed when you use the list shadows command.
- vssadmin resize shadowstorage /for=c: /maxsize=2GB – Sets the shadow storage for drive C to 2 Gigabyte. May delete existing restore points starting with the oldest if space is not sufficient to store all System Restore points