find a guy with a 360, transfer all your files to a brand new hard drive that he buys using the transfer cable, send the whole kit and caboodle back. sell refurbished drive on ebay.
actually, since savegames are all that matter (you can re-download DLC by transferring the license with the license transfer tool...you can only use it once a year, though) just have him get a memory card to save his stuff onto. they're like 20 or 30 bucks.
you can't transfer files to a computer without installing some dastardly i/o device drivers that can really screw with your system. and, last time i tried (a few weeks ago), xp sp3 isn't supported without severe system instability.