How to use or reference the Usbser.sys driver from universal serial bus (USB) modem .inf files

This article describes how to use or reference the system-supplied Usbser.sys driver file from a third-party modem .inf file.

Applies to:   Windows 10 - all editions
Original KB number:   837637


Universal serial bus (USB) modem .inf files can both use the Usbser.sys driver and directly reference the Usbser.sys driver from the .inf file. However, we don't recommend this.

Instead, we recommend the following:

  • Drivers that are distributed with the operating system use the Usbser.sys driver.
  • Drivers that are not distributed with the operating system use the Include directive or the Needs directive. The Include directive is described in the More Information section.

More information

To reference the Usbser.sys driver, we recommend that USB modem .inf files reference the Mdmcpq.inf file.

For example, the DDInstall section of an .inf file uses the Include directive and may be similar to the following:


AddService=usbser, 0x00000000, LowerFilter_Service_Inst


The following sections appear in the Mdmcpq.inf file:

  • FakeModemCopyFileSection
  • LowerFilter_Service_Inst
  • LowerFilterAddReg


For more information, see the "Device Installation" topic in the Microsoft Windows Driver Development Kit documentation.

Data collection

If you need assistance from Microsoft support, we recommend you collect the information by following the steps mentioned in Gather information by using TSS for deployment-related issues.