Under lock and key
The company I worked for in the UK used to keep all the desktops under lock and key underneath the desk. This meant if it needed a hard reset you had to call someone from support to come up with a key. Probably a policy designed to stop third party peripherials being connected and introducing virues or sucking away company data.
It's OK though - we survived - we found that one of the prongs on a power plug was able to fit in the lock and jimmy it open....
Obviously such a lock and key policy doesn't support the notion of turning on/off PCs overnight though.