What are your settings? Are you using the maximum amount of hard drive space? If not or your hard drive doesn't have a lot of free space, it will purge the oldest restore points. Plus, sometimes installing a new program uses all of the system restore space allotted.
Every now and then (ie;after installing a new program) all of my "restore" points disappear on the System Restore feature of XP. It's not corrupted it's that they're gone thus there are no "bold" dates where I created several restore points.
Anyone know what could cause this?