At present we store a lot of information of us in our pc which includes photos,games,some important documents and files and some of our personal photos and videos.We dont want to lose all the data anytime.So its essential to make a backup of these so that they will be available even on corruption of data.There are many ways to back up your data.
1.Back up using external hard drive
2.Using the recently developing online storage
3.Using backup options available under properties menu in my computer
I'm sure you know how to do the first 3 things(if not post comments so that i can explain in detail to you) so I'm only explaining about the fourth part...
DOING SYSTEM RESTORE:
For using system restore you must go to start->all programs->accessories->system tools->system restore
We can use your own generated restore points(specific dates) or the computer itself automatically generates restore point when you install new games or software or hardware or when you do some changes in the system..select any of restore point at which the computer is in proper running state..and then select next and then your computer restarts and then your computer is taken back to its state how it was at that time that you have given at the restoration point..
NOTE:If your xp is corrupted then run xp in safe mode and then do system restore..