if the wireless worked fine in xp, then its obvious that vista is the culprit.
vista is written in a diff code. i've found that pure vista machines can't handle xp if downgraded.
like wise, there are issues with upgrades to vista, moreso, to vista.
if you really need to get down to business, i'd get the dell restore disk out, and go back to xp.
vista will be replaced soon by a new os, in 2009.
vista has been considered the 'millenium' of xp upgrades, just a candy coat.
kj
computer corrections
cookson, ok
p.s.
i sure wish i had the lapper here. i have a 100% fix success over the last 10 yeard. it would be fun