Now whenever system audio plays (from web browsers, apps, windows sounds, or video games) it will play to the JRiver Media Center driver.

Note: If JRiver doesn't show up as a Windows Device in Control Panel > Sounds > Playback, try disabling it in MC General > Features. Because the WDM Driver is now the system default, setting Media Center to output to the system default just creates a closed loop. Make sure that, in Media Center, your setting under Options->Audio->Audio Device is not 'Default Audio Device.' You need to set your audio device to whatever your actual physical output device is.Select the one labelled JRiver Media Center 20 and click the Set Default button at the bottom of the menu as shown to the right. You should see all of the Audio devices on your system listed.

Once the driver is installed, go to the windows control panel, and then to the Sound menu item.

Then restart Media Center and the driver will install. To enable it go to Options->General->Features and check WDM Driver. In versions of Media Center after 20.0.95 the WDM driver is disabled by default.

Windows virtual audio driver