i'd go with ishater, i've built 3 enclosures already, it's really easy, all you have to do is follow the directions, and you can pick your own HD. For me, it's easier for warranty service in case the drive fails.
i picked up an enclosure somewhere (i forget) online for about $45, and a western digital 120 for $80 after rebates, took me about 10 to plug the cable to the HD, power cable, and then the hardest part was the case, which used some plastic strip to lock everything together. my gf was up and running in a short amount of time (after the driver installs, and formatting to PC), backing up her notebook.