Consumers, meanwhile, can start testing the software's new parental control features that enable parents to monitor and control their children's computer use by blocking certain websites.

It can also prevent access to games based on the ratings set by the Entertainment Software Rating Board, and allows parents to set a timer for the maximum duration of computer use. 

The December Community Technology Preview will introduce a new feature dubbed Bitlocker, which uses a technology that Microsoft refers to as Secure Start-up.

Bitlocker will encrypt the contents of the hard drive on a laptop computer, preventing data leaks when the device is lost or stolen.

New performance features include Superfetch, which was unveiled at the Professional Developer Conference in Los Angeles in September.

The technology uses external memory, including USB memory keys or flash memory chips, to boost system performance by preloading commonly accessed data and applications into the memory.

Testers can also expect to start seeing some of Vista's new designs for the user interface, including transparent windows and an updated interface for Media Centre editions.

The preview will be made available to about 500,000 developers and IT professionals through Microsoft's technical beta, MSDN and TechNet programmes.  

Windows Vista is the first version of Microsoft's operating system for which the company is using its Community Technology Previews.

Microsoft promised the monthly updates in September, although it skipped the November release. Each preview is centred around a certain theme, indicating to testers when they can expect to start looking at certain functionalities.

Microsoft issued a first beta of Vista in July. A second beta has been promised for early 2006, and the final product is scheduled for the second half of 2006.