Win7 is graphical appealing and good for multi media, where as, windows xp is plain, non buggy, and doesn't take up as many resources. Not to mention xp options are way easy to navigate. I've been building/networking/troubleshooting pc's for a long time (8 years) and i'd have to say I like both and use both.
My gaming desktop runs xp 32 bit.
ati 4750 1 gig
2 gigs of ram
duo core 2.2ghz amd proc.
Idles at 380mb of ram used
My netbook runs win7 32 bit "starter" edition.
Single core 1.6ghz.
Onboard intel accelerator, 250mb vid ram
1 gig of ram
The netbook, which is what i use for iming and multimedia, performs well and is fun to use. My girlfriends netbook is win xp and works fine aswell though.
Basically If you have atleast a gig of ram and a 2.0ghz processor and your aim is to have a multi media computer, i would suggest win7.
If you have a computer with lower resources or you are a gamer and are seeking a less buggy invironment and lower resource usage, go with xp.
PS. If your running vista i would upgrade, downgrade, or throw your computer out the window, vistas horrible.