You'll need a bigger harddrive if I were you I'd go out and find either a 60 GB harddrive or a 120 GB Harddrive. Just save up the money and you'll be able to find it in a couple months
Those hard drive you mentioned will not work on the 4GB slim.
The hard drives designed for the old 360 will not work on a slim.
The OP will need the 250GB hard drive that was designed for the slim.