System Restore

After many frustrating tries, I finally got XP to boot on my Vista computer. All is well except for 1 problem. System Restore points keep getting deleted on my Vista operating system. I thought it was a 1 time deal when I installed XP, but I created a restore point and when I booted from XP back to Vista it was deleted(2 times). There is no problem on the XP side with System Restore. On both systems I am only monitoring their own perspective hard drive.
Any ideas?