Microsoft has unveiled the first beta of Windows 7, enabling users to test the improved user interface and other features of the forthcoming operating system for the first time.

At the CES 2009 show in Las Vegas, the company also announced availability of its updated Windows Live services for consumers.

Windows 7 Beta 1 is available immediately to subscribers of MSDN and TechNet, while everyone else will be able to download the software from the Windows 7 web site from 9 January. The ISO image file is approximately 2.7GB in size.

"I really believe that Windows 7 is the best operating system we've ever developed," said Steve Ballmer, chief executive of Microsoft. "I encourage you all to get out and download it."

This build of Windows 7 has all the features and user interface improvements showcased at the Professional Developer Conference in October, but which were missing from the preview version distributed at that time, according to Laurence Painell, Windows marketing manager for Microsoft UK.

These include HomeGroup, which is designed to make it simple for users to get Windows 7 computers to find each other and share files such as music and video stored anywhere on a home network. It also includes support for Libraries, to help users organise collections of files, regardless of whether they are stored on the local computer or elsewhere.

Windows 7 Beta 1 also includes touch-based interface support, enabling users with touch-enabled hardware to access their PC using fingertip control. The user interface enhancements such as support for Jump Lists - shortcuts to key functions in applications on the task bar - are also now present.

For business customers, Windows 7 Beta 1 now supports Direct Access, which enables mobile workers to securely connect to the corporate network without the need for a virtual private network, and BranchCache, which locally caches content from remote file or web servers. These features require infrastructure based on Windows Server 2008 R2, however.

Microsoft is advising business users to use Windows Vista as a stepping stone to Windows 7. Because it is expected to be compatible with virtually all Vista applications, apart from low-level tools such as anti-virus software, firms can begin compatibility testing ahead of availability to prepare for a migration to Windows 7.

Painell also said that Windows 7 Beta 1 is feature complete, but declined to indicate whether any further betas will be issued before the final release, expected before the end of 2009.

"I can't comment on this, as it depends on tester feedback whether we need to do a second or third beta," he said. However, he added that Microsoft expects to be adding updated components such as device drivers right up until the final release.

Also available now is the new Windows Live, which includes updated versions of Messenger and Photo Gallery featuring better integration so that friends can get an update in Messenger when a user adds a new photo to their gallery, for example.

Microsoft announced that Messenger will integrate with Facebook RSS feeds within the next few months, enabling users to get updates from this source as well as already supported social networking services such as Twitter.

A new function called QuickAd was also announced, where users can add information from advertisements directly into emails on Windows Live, something that will boost Microsoft's web advertising clout.

Windows Live Essentials will be pre-loaded on all Dell consumer and small business PCs from February, Microsoft said.