Our setup at work is a Windows XP Pro workgroup with 3 PCs and a laptop. I've set up various scheduled maintenance tasks to run on a daily basis - clearing temporary files, backing up data and defragging. The last task to run on each PC is the defrag, running O&O Defrag version 6.0 and the option is set to "Restart and shut down after Offline-Defragmentation".

Sometimes they all shut down, sometimes one or more is left on.

Any ideas please??

If another task is active when the scan finnishes it might halt the shut-down process.

Yes, I thought of that, but it does this in the evening after everyone's gone home, so there shouldn't be anything else running. I made sure it didn't start until well after the backup should have finished.