In Windows XP, the System Restore function performs checkpoints on a number of occasions such as on shutdown, during installing certain programs and when a system-level device driver is installed.
System Restore also automatically writes checkpoints every 24 hours. On some cases, checkpoint writing may prevent automatic system, either passively or on demand. Consider the following circumstances:
Check if the system’s CPU is not idle when System Restore is scheduled to run.
System Restore also automatically writes checkpoints every 24 hours. A new checkpoint will be written every 24 hours while the machine is powered on if a system has been running for more than 24 hours.
Make sure the System Restore and Task Scheduler are running.
The Task Scheduler must be running to ensure the System Restore works properly; that is to create checkpoints automatically every 24 hours. Always make sure that no application, script or user has disabled either of these services.
The Event Log Service has been stopped.
A particular sign for this problem is if System Restore locks up when the user attempts to manually create a restore point. (When a restore point is created manually, an event is logged, so if the Event Log service isn't running this obviously creates a problem.)
System Restore operations is suspended due to situation that occurred.
For suspended operations, circumstances include running out of space on a non-system drive on which System Restore has been enabled; or modification of a file monitored by System Restore on such a drive (for example, an unsigned device driver). You need to reactivate System Restore by manually running it after you've cleared up the condition in question.
Watch out and always make sure to avoid these interruptions to keep the System Restore to work as it should.