Registry values must be set correctly for combo net/modem cards to function properly.
In \Machine\System\CurrentControlSet\Services\DriverName#
\Parameters you must add ModemFunction:REG_DWORD:1 to
identify the combo card. (DriverName is the name of the combo card
driver and # is the instance number.) The first I/O port location, IoBaseAddress,
must identify the modem location. There must be only one InterruptNumber
value entry, identifying the IRQL to be shared by the components of the combo
card.
See the Programmer's Guide for information on installing drivers.