The VIA AC97 Audio Controller (WDM) is a driver for sound hardware based on the AC97 audio codec standard, commonly used in older motherboards for audio processing. It enables the operating system to communicate with the sound hardware. To install it, you can either download the driver from the VIA website or use the device manager in Windows. In Device Manager, locate your audio device under "Sound, video and game controllers," right-click it, select "Update driver," and either let Windows search for it automatically or manually point to the driver file you downloaded. Would you like more details on how to find or install the driver?