All,
I don't know if this will work for you or not but we did find this Regkey:
HKEY_CURRENT_USER\Software\Microsoft\ActiveMovie\d evenum{4EFE2452-168A-11D1-BC76-00C04FB9453B}\Default MidiOut Device\
Find the device you want and check its MidiOutId and put that in the Default MidiOut Device\MidiOutID value.
Let us know if this helps. Also if you can post the maker\program you are trying to use, then we can check on compatibility.
Windows 7 compatibility center