I am just going to be backing up for a downgrade to windows 7 like a couple of games and new drivers I would like it to be at least 100gb and around 50 dollars for a external storage
if you can afford $55 then this will be good http://www.newegg.com/Product/Product.aspx?Item=N82E16822149499
Though you will have to make due with 500GB of storage.
if you need cheaper, and do not mind connecting something as an internal drive, or ripping the case off, you can buy this
500GB for less money, though it is literally a 2.5 inch drive inside of a plastic case, and thus cannot be used unless you have a sata to esata adapter+ USB power connector.
if you can install the drive internally, then buy this and rip it out of the case. (epic fail for anyone who actually needs external storage, but good way to get a cheap 500 gig drive for internal use, or use with a old laptop)