i have been wondering this because the lower console for the Xbox360 (the cheaper one 299USD) says it does not come with hard drive which im aware of but is there a way i can buy a hard drive later on if i choose to get it?, just curious because i saw a hard drive at walmart for the 360 and was wondering is it something that you plug into it and it is external? or is it something that essentially makes it the 399 xbox?