The windows volume shadow copy service is a service which implements a framework to allow volume backups to be performed while applications on a system continue to write to the volumes.  Windows uses this service to create and restore points.  Windows 7 comes with a command line utility called vssadmin. Vssadmin can be use to perform various restore point chores from the command prompt.  The utility does need elevation so first open up an elevated command prompt.

To list all restore points on C drive use the command:

C:\Windows\sytem32> vssadmin list shadows /for=c:

To delete the oldest restore point only use the command:

C:\Windows\sytem32> vssadmin delete shadows /for=c: /oldest