So I read about this yesterday from Slashdot
I know that you can do it from any liveCD linux distro, though I thought it was cool that BackTrack got the publicity. Anyways, I went ahead and tried it out with my copy of Windows Server 2008 Enterprise (thanks microsoft launch tour). It worked flawlesly, and instead of running "explorer" from the Utilman.exe promt, i ran "lusrmgr.msc" and simply added my own administrator account. I got out of utilman, clicked cancel for the Windows login, did a ctr+alt+del and my new TEST_ADMIN account was waiting for me to login.
I wasn't able to do anything once i ran explorer from utilman, except run firefox (from which i was able to browse the net) which i had installed previously while logged into the admin account. it was all so easy...