I thought this was common knowledge, but after a discussion on twitter, and a subsequent internet search, I think it’s not well known. In Windows 7, and Server 2008 and 2008 R2, you can disable UAC without requiring a reboot. You simply have to log in with the local administrator account and disable it via the User Account Control Settings dialog. Any change made will not require a reboot. Please note, you must use the built in Administrator account… using an account that’s in the Administrators group will not work.
It appears that in Windows 8, a reboot is never required, at least I couldn’t get a forced reboot in my testing. If I have time, I’ll update this with testing on a Server 2012 system in a few days.
Note, I am not endorsing that one routinely use the built-in administrator account on a system, and I’m not endorsing completely disabling UAC. Both are very real security risks… but there are times when it’s far more expedient to do this in a controlled fashion than the alternatives. I am a firm believer in the policy of Least Permissions Needed.