Windows XP: Enforcing power policy on non-admin users?

I’m trying to get a lab computer to go to sleep / turn off on its own after a set number of minutes, a simple task on an admin user, but I can’t seem to do it on the public/guest account.

When the guest account is not an administrator, it won’t let me change the minutes at all. When I temporarily make them an administrator, change the power policy, and then switch it back to non-admin, it seems to lose all the changes.

Is there a right way to do this? Can I enforce it through group policy or similar?

I would think so. But the guest account has to be part of the domain, ie. LAB\guest, and the updates, firewall, virus sniffer, and power options are all controlled through the server.

Is the computer networked? Often networks will not allow persistent changes to ACPI settings.

On the chance that XP itself doesn’t allow any non-default settings to persist for the public account, you can edit the local machine registry key. Unfortunately, I’m typing on my Mac right now, and my Google-fu is not yielding confidence-inspiring results for the right edits.

It’s not networked; it’s a standalone system.

Hmm… the HKLM option; would that override HKCU?