i was wandering if anyone here could help, becuase im a bit confused.

On the microsoft site is says that if you have windows xp then you have to
do a clean install, for vista premium. But the guy here:
http://www.windowssecrets.com/comp/070201#story1 says that you have to
install vista twice to do a clean install, so could anyone explain me which
method is correct. Iam currently using Windows XP Pro SP2