The number of restore points is limited by the amount of space set aside
to store them. In any case, restore points older than 90 days are not saved.

Unless you have not used your computer since March I would advise
against using a restore point that old. Restore points contain only a
small number of key system and user files. By mixing such old files with
the current files on your computer you are risking the stability of your
system.

A restore point is not the same thing as a backup. To create a backup
you need backup software. Windows XP has Windows Backup, a rather
rudimentary (by current standards) but nonetheless effective backup
program. Of course there are many third-party backup programs.

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Leonard Grey
Errare humanum est