Could you make it an Screen Saver option to be able to select just drive C: or ALL.
Thanks for sharing your idea, it's appreciated! I'll consider adding something like that to the screensaver. In the meantime you could consider using the scheduler to start the defragger, instead of using the screensaver. That way you can specify exactly which disks you want defragged and other options, and do it all when you're sleeping and will not be bothered by it.