Like bchur83 noted, the XP System Volume Information directory (contained on each drive) contains the "System Restore" points that have been created, as they relate to that drive. Besides disabling System Restore, you could also remove all but the most recent restore point (Start | Run | Type cleanmgr, and click OK | 'Options' tab | 'System Restore --> Clean up' button) on each partition or drive.
AFA the System Volume Information directory in W2K, it's used by the Encrypting File System (EFS), including the partition table information ((the hidden NT filesystem structure.))