Windows XP Install Question?

I have three old computers that are scrap sitting in my attic all with window xp cd keys, I'm putting together a new system this weekend. Leaving me with this question can I install xp on my new system using one of those keys? I know the Eula states one processor per license but can I just remove xp from my old computer and use it for my new computer? I figured I'd ask here because their have been many questions about the EULA and everyone here is knowledgable on the matter.

Thanks,
Mike

do you have the XP disks that go with the 3 systems? If you do then you can install the XP system on a new system with the matching code. If the systems says its already been registered then call MS and let them know you switched MB's.

Once Its up and running then just delete the XP that you used from the old system. That should keep you legal.

Do the discs have to match the ones that came with that system? I'm sure I have XP discs lying around somewhere, I have countless spindels of cd's. I just want to be 100% legal so I wanted to double check here.