520 WMC Data Modem Driver 4.40.2.1

1. Create a restore point(Start → "Create a restore point" → Create), so you can roll back if anything goes wrong.
2. Verify compatibility: your Windows version (Windows 8.1, Windows 8, Windows 7, Windows XP) and architecture (x64, x86)must match this driver, and your device's Hardware ID should appear in the list above.
3. Download the file using the button - it comes directly from Microsoft Update Catalog.
4. Optionally verify the checksum: open PowerShell, run Get-FileHash your-download.cab -Algorithm SHA256 and compare with the SHA-256 above.
5. Extract the .cab archive: right-click → Extract All, or run expand -F:* file.cab C:\driver\ in Command Prompt.
6. Install via Device Manager: right-click your device → Update driver → Browse my computer → point to the extracted folder. Alternatively run pnputil /add-driver C:\driver\*.inf /install.
7. Check Device Manager: the device should show no warning icons, and the driver version should match.

If the device stops working after the update: Device Manager → right-click the device → Properties → Driver tab → Roll Back Driver. If the button is greyed out, use the restore point from step 1 (Start → "Recovery" → Open System Restore).