Windows Media Player displays "error C00D11B1" when the program is unable to play a file. There are many reasons the player might display this error, including problems with the computer's sound device or problems with the file itself.
To fix the problem, first try to use Windows Update to download updated drivers, or check the sound device manufacturer's website to see if updated drivers for the device are available. If this is unsuccessful, try using Device Manager to check the status of the sound device. To do this, search the PC for Device Manager, and open the manager. Click on "Sound, video and game controllers," and look for the name of the computer's primary sound device. If the sound device is listed but has a red "X" next to it, right-click the device, and select "Enable." If the sound device is not listed, click to expand the "Other devices" or "System devices" listings, and check to see if a "Multimedia Audio Controller" appears on either list. If so, right click the icon, and select "Update driver software." If there is no sound device installed on the computer, try to install one, and attempt to play the file again. If attempting to play the file from a link online, wait a while, and try playing the file again later. Server or network problems may be causing the error message.