If your copy of Windows XP is using the NT file system (rather than FAT32) and cannot process all the Input and Output requests as your computer shuts down this may force your PC to restart.
If these restarts become a problem a good tip is to run the Chkdsk tool to repair any problems with your disks volume.
To do this Click START and click RUN and then type cmd in the box. At the command prompt type chkdsk /R /C (i.e. repair your C Drive) and hit ENTER.
If the following message appears: “Cannot lock current drive. Chkdsk cannot run because the volume is in use by another process. Would you like to schedule this volume to be checked the next time the system restarts?”
Type Y and hit ENTER
Reboot the PC and Chkdsk will automatically run and check the drive for errors. It will then attempt to repair these.
This will usually fix the shut-down and restarting problems on most Windows XP machines.

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