Microsoft Windows XP System Restore

The System Restore feature of Microsoft Windows XP (the operating system
previously known as Microsoft Whistler) enables administrators to restore their PCs,
in the event of a problem, to a previous state without losing personal data files (such
as Word documents, drawings, or e-mail). System Restore actively monitors system
file changes and some application file changes to record or store previous versions
before the changes occurred. With System Restore, users never have to think about
taking system snapshots as it automatically creates easily identifiable restore points,
which allow users to revert the system back to a previous time. Restore points are
created at the time of significant system events (such as application or driver install)
and periodically (every day). Additionally, users can create and name their own
restore points in Windows XP at any time. System Restore has an automatic restore
point space-management feature that purges the oldest restore points to make room
for new ones, so that a rolling safety net is always kept under the user, enabling the
user to recover from recent undesirable changes.
System Restore is enabled by default and will run upon the successful completion of
either the Windows XP Professional or Personal x86 version installation. It requires a
minimum of 200 MB of space available on the system partition. If there are not 200
MBs available, System Restore will install disabled and will enable itself automatically
once the required disk space is created.