Yes you can and no you won't be as long as you are only using your copy of XP on a single machine.
You will probably have to re-validate your new machine because retail XP requires you to do so or it stops working. Microsoft exist to help you with this (this is very similar to one of the world's greatest lies - you know - I'm from the government and I'm here to help!). Call them.
But seriously, if you've paid for the licence you can put the OS on any single machine you like.