ATSC only (no NTSC) USB TV tuner - Windows Media Center won't find channels

I have an ATSC only (no NTSC) USB TV tuner (Encore ENUTV-DAT) attached to a
computer running Windows Vista 64-bit Home Premium. Windows Media Center
runs just fine as far as viewing live, recording, and playing TV programs,
but I can't get it to automatically scan for channels through the antenna.
It says it can't find a tuner attached to an antenna. I got Media Center to
set up some of the channels through downloading the Guide for my area, but
comparing the channels to an ATSC TV tuner doing automatic scanning, it's
missing channels because of not scanning through the antenna. I'm guessing
the problem is Media Center thinks I don't have an antenna because it can't
find a NTSC tuner. Does anyone know who to get Media Center to overcome
this problem.

Perry Webb