pwedeng pwede sir... as a matter of fact, i do it all the time...
everytime na magfo-format ako ng HDD ko, i always do a clean Vista installation... that way, wala masyadong glitches sa installation, and at the same time, it cuts the installation time...
ginagawa lang naman usually ang upgrade mode kapag:
1. upgrade version ang winvista mo, which is not always entirely the case... the vista DVD, regardless of version [home basic, home premium, ultimate et. al.], is bootable, and can be used to do a clean install...
2. there are no drivers present for your devices to run in winvista... install ka muna xp SP2, then drivers ng xp, then upgrade install ng vista...
ang alam ko, pag maguupgrade ka from XP to Vista kelangan, at least XP SP2. Pero pwede ding clean install na lang para maginstall yung Vista.
So far, XP pa rin talaga ko, due to my computer specs. pero, given the choice, gusto ko Vista na. hehehe