Can't Install External Hard Drive

Sorry to piggy back on your question but can't get a new question started.

I've got a similiar problem. WD HD in a Vantec USB2.0 enclosure. When I plug
it in NOTHING happens. Doesn't even try to install drivers. It's like nothing
is hooked up.
Out of desperation I put the HD in an external DVD case and formatted it on
the same system running Vista. No problem. The problem seems to be the
enclosures (this is the 3rd and different one). It works fine on Windows 2000
machine.
All other USB2.0 devices working fine.
I"d give my left you-know-what for a solution. I need the external hard drive.
Thanks.