You can read Microsoft's full Q/A section about System Restore for Windows XP, including facts and instructions, by clicking here. To summarize, it is a utility (accessable from the start menu) which allows you to ''roll back'' your computer to a certain time incase the installation of a program or modification of certain files/settings caused a problem. Using it will remove any programs you've installed since the restore point, but leave all personal files alone. However, it is not an all-in-one solution, so it's always best to be careful of what you install/modify, and always keep backups.
Hope this helps,
John
Alright people, prep yourselves for another ridiculous
"Newbie" question- "What is System Restore and how do I use it?"
Many thanks for your information and patience!
granpama

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