Why can't regular users shutdown Windows Server 2003?
Perhaps this is obvious for a production system - you'd hardly want end-users to be able to shutdown the server.
If you're using a Windows Server 2003 system on a laptop as perhaps a demo, dev or test system then you may want regular users to be able to shut the system down without having to log off and back on as an Adminstrative level user (or use "MakeMeAdmin").
It's easy to grant users the right to shutdown the system - simply log into the system as an account with Administrative rights, Click "Start", "Administrative Tools", "Local Security Policy" (or add the MMC snap-in) then select "User Rights Assignment" followed by "Shut down the system". Finally assign the right to the user or group of users.