Possibly applicable:
Restore Points Are Not Saved in System RestorePossibly of Interest:
Description of the System Restore Utility in Windows Millennium EditionSome quotes from the
System Restore FAQQUOTE
Typical reasons why checkpoints are not being created:
• System Restore requires Task Scheduler to create system checkpoints. If Task Scheduler is disabled it will prevent System Restore from creating system checkpoints on a scheduled basis.
• System Restore requires the computer to be in an idle state to create system checkpoints. This is by design so that System Restore does not interrupt a user by taking processing power. If computer is never idle, system checkpoints cannot be created. Also, check for any applications that run on the computer during idle periods, such as a virus scanner.
• Another cause may be that the computer is in continual use for limited periods and then shut down or put into hibernation, preventing System Restore from creating restore points.
QUOTE
Why are my restore points missing or deleted?
• If no free disk space on monitored system drive or on any of the available non-system drives exists, System Restore will purge restore points consistently across all monitored partitions to free disk space. If the free disk space falls below 50 MB on any monitored partition, System Restore will stop monitoring and suspend.
Note: Some users have reported that using the Real Player One utility has deleted restore points. Please review your System Event Viewer log for System Restore events for a volume error event.