if you want actual security, air gap is the way to go. why even connect it to the 'net just for a few bins?

no windows xp flaw could ever be exploited, as long as all you're doing is transferring stuff on a usb stick or something

that is, if keep your MAIN machine virus free, so the usb stick doesn't become infected (although disabling usb autorun on the xp machine kills off 99% of those viruses..)