U.S. Robotics Fax Modem Models USR5638, USR5639 and USR5670 dropped from Windows 11/10.
The following internet dial up and fax modems were disabled in a January 2026 Windows Update. 56K V.92 PCI Express Internal Dial-up Faxmodem – model USR5638, 56K USB Internet Dial-up External Softmodem – USR5639, and Internal Internet Dial-up Faxmodem 56K V.92 PCI model USR5670 have been discontinued by Microsoft.
In January 2026, these modems were impacted by Microsoft’s removal of an LSI modem driver due to a security issue. Since these models relied on this driver, they are no longer supported on Windows 10 or 11. No replacement driver is available for Windows.
More information here https://www.getfaxing.com/2025/10/29/lsi-agere-lucent-fax-modems-disabled/
Replacement modem for USB model is available at https://www.getfaxing.com/shop