Microsoft has released an update to its Windows Vista Beta operating system.

The new version is referred to as build 5472 and marks the first update since Microsoft ended public availability of the software.

The release is available to a group of about 500,000 testers who have signed up to the Windows Vista Technical Beta programme, Technology Adoption Programme and Microsoft Developer Network.

The update offers performance improvements, bug fixes and feature enhancements  requested by testers of earlier versions.

The new version improves the responsiveness of the Media Centre features in the software, and introduces support for Media Center Extender technology that allows consumers to access media on their computers through the Xbox 360 or standalone Extender devices.

Microsoft also unveiled a new pre-release version of its Windows Vista Software Development Kit that allows developers to craft applications for the latest Vista build.

Windows Vista is scheduled for public availability by January 2007. A first release candidate has been promised for the third quarter of this year.