I have found the answer ("No") here:
http://www.microsoft.com/technet/prodtechnol/winxppro/plan/faqsrwxp.mspx
"Q. Can I make System Restore permanently retain a restore point?
"A. System Restore is change base tracking tool, not an imaging or
backup tool. Each restore point only stores changes to the system since the
creation of the previous restore point to minimize space usage and improve
performance, and all restore points are associated. Therefore, restoring the
computer from the current state to a previous state requires the
availability of all restore points. For example, if a user wants to restore
the computer from point D to point A, System Restore will evaluate the
system change logs for points C, B, and
"If a restore point is permanent, space usage for storing the complete
chain of restore points since the creation of the permanent restore point
would become very large and impractical. System Restore also provides a
space management feature to purge old restore points to make room for new
ones, creating a rolling safety net. Restore points over 90 days are purged
automatically by default."