This question was about devices which _have_ serial number, to disable new
instance creation when a device with a different ser# is plugged in (during
production and testing, for example). Such a feature already exists.

"David J. Craig" <Drivers@nospamyoshimuni.com> wrote in message
news:%23RH9sygYDHA.2020@TK2MSFTNGP10.phx.gbl...