I would guard against installing Windows XP on newer machines. Firstly, newer machines have Windows 7 as a disk image on them rather than shipping with a CD (they want you to burn your own copy if you need to reinstall it), so simply blowing away the installed OS could leave you without the ability to install W7 easily.
Secondly, laptop manufacturers are stopping supporting XP, which means they won't have a page of drivers ready for compatibility with XP for the newer hardware inside their laptops, so it will become a progressively harder task to get your laptop to work with XP.
Finally, W7 is SO much better than XP. You should be able to hit the ground running.