I had this hd in an older hp laptop that had duel hd's and am no longer using the laptop. It works when I plug it into the 2nd slot of that laptop but when I try to use it as an external hd it is not seen via usb.
It may be an issue with the housing, did it come with a USB cable, some require a Y cable for additional power. Did you reformat the drive when it was attached to the laptop, if not it may be worth a try.
Also, double check your connections for the drive inside the housing.