Which Service/Process Keeps Restarting My PC Daily?

The computers we use at my job run Windows XP Professional. The computers restart at exactly the same time each morning at 5am. What I'm trying to do is learn as much as possible about what is causing the restart so that I can prevent it.

There have been times where I'll be working on a very important project, the computer will restart, and I will lose significant progress. It isn't the sort of work where you can just hit "Save" and continue where you left off after the restart.

If there is a process running that is causing the restart, I want to be able to identify it so that I can "End" it when necessary. If the restart is being caused by a Windows service then I want to be able to identify it so I can "Stop" and/or "Disable" it when necessary.

I will tell you what steps I've taken and what I've learned. I'm hoping that someone can provide some insight or advice on what I should try next.

Note: I have administrative rights. All steps taken were done with admin privileges active.

a) I've tried the "Start>Run>shutdown -a" method in an attempt to halt the restart when it begins. It didn't work. The restart still occurred at 5am.


b) I tried changing the Windows clock in an attempt to delay the restart. It didn't work. The restart still occurred at 5am.


c) I tried disabling the Windows Time service in Control Panel>Administrative Tools>Services. It didn't work. The restart still occurred at 5am.


d) I tried methods b and c simultaneously. It didn't work. The restart still occurred at 5am.


e) I thought that the restart might be triggered remotely so I disconnected the Ethernet cable from the computer. It didn't work. The restart still occurred at 5am.


f) I tried looking into Control Panel>Task Scheduler to see if the restart was a scheduled task. It wasn't.


g) I tried looking more deeply into the Task Scheduler via the command prompt to see if perhaps there was a scheduled task that was being hidden from the Task Scheduler GUI. There wasn't.


h) I tried looking through the list of running processes (over 50) in Task Manager to see if any of the names seemed like they might be related to restarting or shutting down etc. but nothing stood out.


i) I tried making a list of all processes running before 4:30am to see if any new processes were started between 4:30am and 5am. This wasn't helpful.


j) I tried downloading and using Process Explorer in the hope that it might be able to identify the process that's causing the restart. If the program is capable of doing this then I'm not sure how. Process Explorer seemed to provided a lot of information on each process but nothing that helped me uncover what the intended function of said process was.


I've been trying to solve this puzzle for weeks now. The more time I invest in it, the harder it is for me to give up. Any help would be greatly appreciated. Thank you so much!