Shutdown reason codes are reason codes, not error codes or HRESULTs

A customer liaison asked the following question on behalf of his customer:My customer is finding that their Windows Server 2003 system has restarted, and they want to find out why. I've found some event log similar to the ones below, but I don't know what error code 0x84020004 is. I've searched the Knowledge Base but couldn't find anything relevant. Please let me know why the system restarted.