I'm going to have to do this too.
Once I get Windows Vista, I'm just going to find an application where I can install Windows Vista absolutely fresh, and just freeze it on my HD, so that if something goes wrong (and things always go wrong for me) I can just somehow make that stuff load up and then I won't have to re-activate windows. Especially if Windows Vista starts sucking, I might be going back and forth between Linux and Windows again.
Just too much of a hassle. The sad thing is, they still haven't stopped people from pirating their software... they practically give it away for free to anyone with any computer knowledge on the subject.
But yes, i was reinstalling Windows XP from the XP disc, so what you might be doing might not have any affect on it.
Just be sure if Windows tells you to re-activate your product, that it seems like you only have a certain # of times to do it before they deem your license stolen or given away, and then they say it's your fault or some BS.