hard drive in external iomega cd-rw case?

Hi,
I just got a 7200 WD 250 gig HD. It is not partioned or formated yet
and for the time being, I would
like to enclose it in my usb2.0 iomega cd-rw case. When I plug it in to
the computer, the hardware
wizard runs but It doesn't properly install. The device manager has a
yellow
exclamation point next to the usb drive.

http://www.largeprojections.com/hd/

Does anyone have any ideas on how I can get this to work properly?

Thanks,
Chuck