Lots of turn on/turn off
One of my daughters' has a laptop with a dead battery. Thus it needs to be plugged in for it to work. It was in the middle of the SP2 install process - no idea where in the install, when someone unplugged it. (Probably the wife, who hates to see elec. wasted).
Anyway, same symptoms as your friends.
I thought that I'd need a techie, but it sorted itself out over about 24 hours. I have no idea why. All I did was turn the power off each time when it ceased doing anything. The time it took to cease doing anything at all seemed to vary. I probably turned it off/on about 5 or six times. (The standard help desk response is always turn it on/off a couple of times). (10+ sec.s on power button method of turnoff). Eventually, it took itself to the screen where it says words to the effect "Installing, stage 1, do not turn off". It still took bloody hours to install. I turned it off/on again a couple of times, de-fragged - more hours - and now it appears to be OK.