The way the computer responded when you pressed F2 sounds like it was waiting for your input, and either F2 was one of the answers, or it was "hit any key to continue". Are you certain that there was no sign of a prompt when it hung?

Eventually you'll have to work up the nerve to reboot the thing. You could take another look for a prompt. And I'd be curious what happens when you press F12 instead of F2--a different outcome would pretty much confirm my theory about waiting for input. Which would gratify me no end but might not be overly helpful to you...

I'm not familiar with how the latest Windows handles disk problems (I just got a new computer and went directly from XP to Win7, but luckily haven't fried the hard drive...yet). I wonder if it was asking permission to run a disk scan? Have you run one manually? If not, you might do so before you reboot...which will probably result in scheduling it for the next reboot, which will at least provide a refreshing variation on the dismal theme.

Pretty vague stuff...good luck, man!