By default, Windows Vista/7/8's UAC prompt is shown on a secure desktop. Unfortunately the Print Screen key doesn't seem to have any effect when viewing the secure desktop. I can see the reasoning behind this - no user-mode application should be able to capture the contents of the secure desktop.
However, my question remains: is there any way to get a screenshot of this desktop?
Edit: perhaps it would help if I explain the problem.
I am currently running Windows 8 and I have a small DisplayLink-based monitor that I would like to use. This driver was just released and works great - except it breaks on the secure desktop. I want to post a bug report on the forums there and in order to do so, I'd need a screenshot. Obviously the problem won't manifest itself on the standard desktop - and running Windows in a VM is impossible because Windows 8 requires hardware virtualization (which I don't have) and getting USB monitors to work with a VM is tricky at best anyway.