Microsoft use activation codes for XP - I like to periodically take my system back to basics and re-install all my software etc. So the activation system had me worried (plus formatting your harddrive and then re-loading all the software/drivers etc is very time consuming!). The way I get "around" it is to use a backup program that snapshots my entire harddrive onto DVDs. One such program that I would recommend is Image for Windows (
http://www.terabyteunlimited.com/imagew.html), it is shareware and I have heard excellent reports on the support responsiveness.
It will capture all your harddrive (or disk partition - whichever you select to backup) - this includes the "activated" software. Since I started taking snapshots of my computer(s) I haven't once had to "reactivate" my XP O/S. Of course, one day I will have to as Microsoft are very sneeky and link their activation checks to the hardware the software is installed on, so if you change (upgrade) your motherboard, harddrive or video card the software will demand another activation code from Microsoft. I have never been able to get a correct number on how many times you can activate XP before Microsoft say "no more, you must be pirating that copy" - I have heard various numbers thrown around like 8 or 11, but I'm not sure enough to keep using them up
I personally use Norton Ghost 2003, this is after disasterous results using Drive Image 2002 (which the latest version of Norton Ghost is based on! Semantec bought the company that wrote Drive Image. So I recommend you don't use it!!!!) So if you can get your hands on a copy of the 2003 version (computerfair or whatever) then that is OK too - but I can't recommend the latest Norton Ghost due to its base codeline and also reports I have read on the Internet.
Goodluck,
Peter