In the Reader to Reader article "Flawless Automatic Shutdown of Client Computers" (November 2006, InstantDoc ID 93262), Milos Puchta described a problem he was having with a batch file that was supposed to shut down Windows XP Professional machines running ALWIL Software's Avast! antivirus software. This software prevents users from logging off when there's a disk (e.g., CD-ROMs, USB flash disks) in one of the computer's removable disk drives. Milos discovered that sometimes users left for the day, leaving disks in those drives. As a result, the shutdown process failed and the computers were left on all night.
Milos solved the problem by using the Shutdown command in a batch file. Another solution is to use PsShutdown, a free command-line utility (http://www.microsoft.com/technet/sysinternals/utilities/psshutdown.mspx). You can configure each PC with the PsShutdown utility (copied locally through a logon script if needed) and use a scheduled job with the appropriate command-line switches. You can create a job file on one PC, then copy it to the other PCs. If you don't need to shut down a particular PC, you can delete the job file by using a logon script. PsShutdown doesn't require the computer's name (it assumes the local PC), so using this utility would save Milos time because he wouldn't have to configure batch files.
For remote machines, you can copy PsShutdown and the job file by using commands such as
Copy shutdown.job \\labpc01\c$\windows\tasks
Copy psshutdown.exe \\labpc01\c$\windows\
To run these commands, you need administrative rights on the lab PC and there can't be any local firewalls.
Alternatively, Milos can schedule a job or use a Group Policy shutdown script to shut down the Avast! service prior to shutting down the XP Pro computers. (This is assuming you can't configure Avast! to ignore CD-ROMs or USB flash disks on shutdown.) Once again, this can be done remotely if needed. By shutting down the right service, it should stop the problem of machines not shutting down because CD-ROMs or USB flash disks were left in PCs.