System Shutdown in our window server 2000

Check out this message prompt in our Windows Server 2000.
System Shutdown
This system is shutting down. Please save all work in progress and log off. Any unsaved changes will be lost. This shutdown was initiated by NEPTUNEAdministrator
I have been disconnected in our server four times, so I wonder if the problem is my network or our server. I check my LAN and its fine. I checked our server and suddenly a message box appears saying, "This system is shutting down…" Why our server is shutting down on its own?
We really need your help.
