The warranty is probably through Dell - who by the way, is usually very good with warranty stuff. Buy.com may take a return during the first 30 days or so, but I doubt they do warranty work.
As for giving the wife a computer, my situation is the opposite. My wife wanted her own computer because she was sick of ME messing up our computer all the time... You know, the constant overclocking, OS reinstalls, beta drivers, etc...