You may have heard about a serious issue with the Windows 7 beta that results in your MP3 files being corrupted. Well just in time for the public beta to officially be released, Microsoft has released an update that is supposed to resolve this issue. It also resolves some other smaller scale issues that will be of high importance to Media Center users. Here is the overview from the Microsoft Download Center:

Install this update to resolve live and recorded TV issues in Windows Media Center, recorded TV playback issues in Windows Media Player, and MP3 file corruption issues in Windows. After you install this item, you may have to restart your computer. This update is provided to you and licensed under the Windows 7 Pre-Release License Terms.

The 32-bit version can be found here and the 64-bit version can be found here.