I stole the following tip from Delete All But The Most Recent Restore Point In Vista:
System Restore is a handy feature but it can take up several gigabytes of hard drive space. You can reclaim the space but disabling System Restore, however, by doing so, you will not be able to restore your computer to a given point in time.
An alternative, or happy medium, is to delete all the restore points, except the most recent one. To accomplish this in Vista:
- Click Start, All Programs, Accessories, System Tools, and click Disk Cleanup.
- Click Files from all users on this computer.
- If prompted, click OK.
- From the dialog box that appears, click the More Options tab.
- From the System Restore and Shadow Copies section, click Clean up.
- When prompted, click Delete.
Click OK.