I had an activated copy of Windows XP Home on my pc(Legal version) that was activated. I wanted to put a copy of another pc.
This second pc was completly different specs to the first one. Different board, cpu, hard disk, video, sound, nic.
So, I took the hard disk from the second pc and installed it as a slave on the first pc.
I copied everything from the first hard disk to the second. I removed the second hard disk and put it back in the second pc.
After booting up I got a BSOD, which considering I was using different hardware was pretty obvious.
So, I booted using the xp cd, chose the recover option from the boot up menu. XP repaired itself and started fine.
But it didn\'t prompt to be re-activated.
I have no idea if this will work for anyone else, but could be worth a try.