Does Windows need washing?

Scenario: Computer is shutting down and rebooting at sometime between 11:00pm and 7:00am. It is attached to the internet via ethernet and has a satellite serial link. Several proprietary programs run on this PC using it as a server. It also doubles as a workstation. There are two other PCs on this network. They are turned off at night. The PC being benched is a late model, big processor, big RAM running Windows 2000 Pro. Good machine.

If I bring it home and put it on the bench, turn off all the specialty software, and it runs for two days in a row without a glitch (the mouse cursor never moved & and keyboard never touched) wouldn't it be safe to assume that either the proprietary software or some event sent by internet or satellite is triggering this reboot? Am I missing something here? Take away it's googlymoogly software and outside influence and it is stable, doing its Windows thangy. We have a solution, Houston! Well, at least a direction in which to proceed.

The automatic dog walker, trash compacting software, make lovey-dovey to the spousal unit application, mojo grillin' sauce maker, etc., are all turned off. Hmmmmmm. Methinks 'tis not a Windows or hardware prob. U think?

"Every so often, I like to stick my head out the window, look up, and smile for a satellite picture."
-Steven Wright