There will be six versions of Vista - three for business, two for home use and one for developing nations. The price of the software will range from $100 to $399, Microsoft said.

Holiday sales worries

However, the January launch means that the firm could miss out on the lucrative Christmas marketing period.

As a result, Microsoft is offering coupons for free or discounted versions of Vista to customers who buy a PC with the older Windows XP installed to convince consumers to buy computers over the holiday period.

Microsoft has estimated that the new system could trigger a rise of 10% or more in Windows PC software sales in the financial year to 30 June, with most of the increase coming in the second half of the year.

Vista is the long-awaited update of the Windows operating system that was originally slated to be released in August 2006. The software has been under development for more than five years.

The software is a major overhaul of Windows and updates many of the core technologies. New elements include improved security, an improved 3D interface, plus new sound and networking technologies.

Microsoft has already released information about what PCs will have to do to run the software. Many PC makers are now selling "Vista-ready" computers.

In the US the software will be unveiled by Microsoft boss Steve Ballmer at an event at the New York Stock Exchange.