|This is a screenshot of PCI Tree on a system with the Zoom 3025 V.92 modem. PCI Tree shows the real chipset & maker (1646 - AT&T Microelectronics/Lucent) as well as the PCI ID of the modem. In Windows, a modem requiring an OS-specific driver (ie, Win Modem or Software Modem) will allow a driver only if the PCI ID (and in some cases, Sub-ID) is defined in the .inf file of the driver package.
Once you have this PCI information - you can also get more information about the chipset from
PCI & Vendor Device Lists
In newer versions of Windows, you can also get the PCI ID information from the Modem Properties Screen. (Control Panel -> System -> Hardware -> Device Manager -> Modem. PCI ID is in the 'Hardware ID' field:)