Something messed up the MPEG1 decoder (audio decoder).
AFAIK only some codec packs do that. If you can't uninstall the codec pack, try (As a sugestion, I am not sure is working) to install matrix mixer. And if it solve or not the problem, please write here an answer. Thx.
SOme codecpacks when uninstalled mess upthe codecs and the sole solution is a Windows clean reinstall. Nothing else worked.