Hi,
I'm running Vista Ultimate x64 and have been doing so for a couple of months. It's been activated all the time, but today it popped the "Windows has detected a change in your hardware and needs to be activated" which seem very odd to me since it hasn't changed.
I had some BSOD's due to my RAM not getting enough volt's, so I took the sticks out and re-inserted them, but I still run the very same RAM sticks.
This is the second time it asks me to reactivate Vista, and the first time I had done even less changes than those above, all I did then was shutdown over night, and when booting the day after it wanted me to activate an already activated license without any hardware being changed.
Cheers