[quote name='K_G']You can crack open the old style drive enclosures and remove the hard drive and then stick the hard drive into the slim. Alll you need is the right screwdriver/bit...I think it is a torx screw, although off the top of my head, I'm not sure which size it is. The exposed drive is smaller than the space for it in the slim, so it isn't well supported in the space, so you need to be careful when moving the 360. Or you can buy a knock off slim enclosure (which is just a price of plastic that holds the drive in proper position...the hard drive directly interface with 360 slim) off ebay for about $10 shipped. I did this a few months ago with old drive and xbox 4GB and it has worked out quite well.[/QUOTE]
As he eluded you don't need the plastic thing, the drive fits in really sturdy without it. The torx things a pretty cheap.
I have a set and would haply disassemble and sell the 120GB Elite drive I just got for $32 since I don't actually need it. Probably will end up eBaying it otherwise.