every day at the same time (3:00 o'clock AM you said) then it sounds like it has been scheduled to do so.
Look over this link and see if you have any scheduled task running the command shutdown.exe -r -t 00
If you do disable it.
If you are using Windows Server Update Services (WSUS) at your location the default time for the scheduled install is 3:00 A.M. once a day, and if an update requires a reboot in order to complete installation, the client will automatically reboot (if some update keeps failing to install it could cause the daily re-boot). In that event this might help but you would still have to hide the update so it wouldn't be attempted. http://technet.microsoft.com/en-us/library/cc512630.aspx
My computer is running on Windows XP and I use Nod32 as well. after refresh installing my windows the problem came up(and upgrade bios firmware). the computer automatically restart at 3 am ??!!
I thought that it's because of automatic update so I disabled windows automatic update (and enabled the related policy for preventing automatic restart as well).
but I still have the problem.( I have unchecked automatic restart for system failure).
How can I find where the problem stem from?
is any software to track down the problem.
Thanks in Advance