Sometimes you can be tying to determine what has gone wrong with your computer can be difficult if you can't see the particular error because the system is automatically rebooting. This can be switched off, and should generally be switched off by default, but strangely enough, it isn't.
XP Users:
Right click My Computer and select Properties.
In the new Window, Select the Advanced tab.
In the Startup and Recovery area, choose Settings.
Uncheck the box next to Automatically Restart under System Failure.
Click Apply then OK.
Vista Users:
Right click Computer and select Properties.
In the new Window, select Advanced system settings on the left menu.
In the Startup and Recovery area, choose Settings.
Uncheck the box next to Automatically Restart under System Failure.
Click OK.









