Windows Media Player may not be able to play a portion of content that you select because that content requires a codec that either could not be downloaded to your computer, or is not supported by Win MP. By default, Win MP downloads codecs automatically when you need them to play a file.

When you are trying to play back content, temporarily set the Internet Explorer Download unsigned ActiveX controls security setting to Enable or Prompt. This setting will let you install the codec.

1. In Internet Explorer 4.x, click Internet Options on the View menu. In Internet Explorer 5 and 6, click Internet Options on the Tools menu. (Or go to Start > Control Panel > Internet Options).

2. On the Security tab, click on the Custom Level... button.

3. Scroll down to Download unsigned ActiveX controls and click Enable.

4. After codecs were downloaded, follow again steps 1-3. On step 3 change your settings back to Download unsigned ActiveX controls, Disable.

Note: If you want to avoid step 4, select Prompt instead of Enable. In this way, you'll always be notified of new "unsigned downloads".