Laptop can’t ‘see’ external USB HDD

Hi all, this is probably a lame question, so bare with me. I just bought a generic USB external HDD enclosure and have a 40GB laptop HDD in it. Its USB 2.0 and works with my new laptop just fine. When I plug it into an old laptop however (with only USB 1.0 ports) it installs OK and is showing as working OK in the Device Manager, but the drive isn’t listed in My Computer. There seems to be no way to access the drive. I’ve tried uninstalling and reinstalling – works fine every time but I still can’t see it.

Any ideas? Thanks.

Louise.