After reboot from a manual shutdown (START->Shutdown) the Windows System Eventlog shows two events 1074. The first entry contains the correct reason code provided by the user, the second looks similar to this:
Log Name: System
Date: 7/29/2009 12:00:26 PM
Event ID: 1074
Task Category: None
The process C:\Windows\system32\winlogon.exe <computername> has initiated the power off of computer <computername> on behalf of user <computername>\Administrator for the following reason: No title for this reason could be found
Reason Code: 0x500ff
Shutdown Type: power off
Event 0x000500FF (System Failure) is written to the SEL (System Event Log) even if a different shutdown reason was provided by the user who initiated the shutdown.
Microsoft has confirmed that this is a problem.
Microsoft will address the problem in future releases.
Use shutdown.exe to initiate the shutdown. E.g. from the elevated command line run:
shutdown.exe /r /d P:4:2
This will result in an eventlog and SEL entry with reason code 0x80040002.