Perhaps some may be interested with my recent encouraging experience with Windows activation. I had an oldish desktop. I had originally installed Windows XP-Home SP-1. This had been updated to SP-2, followed by an upgrade to a larger disk. At that time, I had not problem with re-activation.
Recently the motherboard on this unit failed, but the hard disk was fine. I bought a new modern desktop with a large SATA disk installed, but started by installing the old ATA disk. To get it to boot OK, I had to do a Windows repair, which required re-activation. So we have a computer on which only the hard disk is part of a previous activation. But the activation went through without question or delay.
I then installed a splipstreamed XP-Home SP-3 on the SATA drive, while leaving the old hard disk as secondary. When it came to activation, again, no problem or delay, even though I was still using the product key from the original SP-1 CD. So I effectively over a few days moved Windows from an old unit to a completely new one, but encountered no problems or questions in activation.
I had assumed that I would have a problem during at least one step of this process. That I didn’t was a very pleasant surprise! 
Chris
