This driver is for the AC'97 codec only. It will not work for modern "Realtek High Definition Audio" (ALC series) hardware. Installation Instructions

Check the BIOS/UEFI settings to ensure the "Onboard Audio" is enabled and set to "AC97" mode rather than "Auto" or "HD Audio."

Download the WDM_A406.exe (or similar) package from a reputable archive site, as Realtek has moved these to their legacy repositories.

Right-click the installer and select Run as Administrator .

Windows 98, Windows Me, Windows 2000, Windows XP (32/64-bit), and Windows Server 2003. Limited Support: Windows Vista and Windows 7 (32/64-bit).

On newer versions of Windows, you may need to disable Driver Signature Enforcement to install this legacy software.

Ensure your motherboard or sound card uses an AC'97 chipset (like the ALC650, ALC655, or ALC850).