...those ''some users'' (employees ?)can't obey a simple instruction to do so, surely they will disregard other instructions ? So, even if it is possible to do that at Task Scheduler, you still will have a lot of problems ! Anyway, have a look HERE. If that does not work, you may need a third party application.
Is there a way to use task scheduler to force a reboot on XP machines? We have some users that refuse to shut down on required days and it creates major problems the following day.
Any help would be greatly appreciated

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