Originally Posted by yvesj
You don't say the service pack level of Vista. But I would recommend just using CCleaner. It now has a function to remove all but the last restore point, same as on the 2nd page of Disk Cleanup. Also Vista does not have the slider to limit the Shadow Copy storage as XP(restore point space limitation as percentage of drive space) and W7 has.
In Vista you can do it using an Administrator Command Prompt with this command:
vssadmin Resize ShadowStorage /For=C: /On=C: /Maxsize=24GB
(The example sets the limit at 24GB. Just substitute the number you prefer.)