I bought a HDD for my son's 360 and I didn't know which one I needed. Lo and behold I got the wrong one. I now have a brand new, never used, 320 GB HDD for the X-box 360 original model. I would like to offer it here for sale. $50 firm.
Hi there I done the same but all I did was take it apart and bought the empty case for the newer xbox and put it in. You can buy them cheap enough on eBay a few dollars. Just a thought if it doesn't sell and I bet your son would love it as mine is always complaining he's had to delete one of his games he wanted to keep.