The System Restore feature of Windows is used to return your computer to an earlier saved state without loosing any data files if you have system problems or other failures with your computer. System Restore will take an image of your computer at a given place in time and save it as a restore point. 

   System Restore will take these images or snapshots at times before system changes are made to your computer such as program installations and updates. These snapshots are done without user intervention. You can also create a restore point manually if you feel the need.
   In order to get to the System Restore option - Click on the Start Button -> All Programs -> Accessories -> System Tools ->System Restore. You will then see the "Welcome to System Restore" screen with the default option already selected "Restore my computer to an earlier time". Click on the Next button to continue - you will get a screen that looks like the image given below:

   Sometimes, you may not be able to run System Restore because the computer cannot start up in the normal way. You still have a wide range of options. First - get to a screen called  Windows Advanced Boot Menu Options" - the easiest way to get there is to restart your computer, count 02 seconds and start tapping on the <F8> key on your keyboard.

    Start up your computer  in Safe Mode / Safe Mode with Command Prompt and run System Restore from the Command Prompt by typing:

%systemroot%\system32\restore\rstrui.exe (at the Command Prompt.)

(%systemroot% is the same as C:\Windows - it is the folder where the Windows files are installed.)

   While you are doing this, you may be prompted to select the Operating system in your computer (select Windows XP here) )and also to enter your username and password. You should have Administrator rights in your computer to do this.

   To use System Restore you will need at least 200 MB of free hard drive space on your computer which shouldn’t be a problem with today’s large hard drives. You can increase this limit to stay on the safe side by right clicking My Computer, selecting Properties and then click on the System Restore tab. You can also turn off System Restore from here if you need to.
  To create a manual System Restore point, click on Start, Programs, Accessories, System Tools then System Restore. Then you would click on Create a restore point and click Next. Next give it a descriptive name. Windows will automatically add the time and date. Finally click on Create.

   To restore from a previous restore point you would click on Restore my computer to an earlier time instead of Create a restore point. Click on Next and you will be presented with a calendar view of your available restore points.

   After you click on Next again you will see a message telling you that Windows will need to shut down your computer and that you should close any open programs. It also tells you that you will not loose any documents you have worked on since the restore date. At this point your computer will shut down and Windows will do its thing. After its complete you can review the stability of your system andif it looks good then you are ready for work. If not you can choose another restore point or undo the restoration.