Hi Catweazle,
Forget the second part of my last post. I was temporarily bamboozled or something!
I just hooked the computer up both ways with these results - the same as the last time I tried it.
With 120V coming in, the front panel green light comes on with the start button light flashing. I hit the start button and the front panel red light comes on (if I remember right, that's the hard disk) and nothing else happens. No noise from the hard disk.
With 220V coming in, the same thing happens, except I have noise coming from the hard disk. But still no startup. But there also should be no difference in the two - this power supply is supposed to change according to the voltage input.
I don't know what's going on with this thing. From the markings on the PS it should work the same way the PS's work on my notebooks. I've travelled all over the world with them and no matter what voltage I put in (with the right adapter for the wall plug) they work no problem.