This from a thread at http://www.daniweb.com/techtalkforums/showthread.php?t=14015&page=2&pp=15&highlight=codec%27s from one of my previous posts on a simular problem.
Putting my "engineering" hat on, consider this:
Windows makes extensive use of CODECS (coders/decoders), as mentioned by DMR above, to support the variety of multimedia applications available. For example, video capture requires numerous codecs to encode the audio and video streams being passed to the PC. As another example, audio playback requires one codec for each type of audio format. In many cases, you may find more than one copy of the same codec on the same system. This can easily happen as various multimedia applications are installed and removed. When there is more than one instance of the same codec, conflicts may result that impair the performance of your multimedia applications.
Whenever you encounter trouble with audio recording, playback, capture and so on, always check for duplicate codecs under your Multimedia icon:
1- Click Start, highlight Settings, and then select Control Panel.
2- Double-click the Multimedia icon, and then select the Devices tab.
3- Expand the Audio Compression Codecs entry and look for duplicate entries.
4- If you see duplicate entries, check the Properties for each instance and then remove the OLDER instance.
5- Apply your changes and reboot the system if necessary.
6- You can check for duplicate codecs under the other entries as well.
Check for duplicate audio codecs which may cause conflict.
