Free copies of some of Microsoft's office software will soon be available. Microsoft said it would make ad-supported copies of the Works package available within "months".

The programs will not run in a web browser but will be installed on a PC and have their cost offset by running adverts while in use. Microsoft said the service would debut with Works 9.0 that was due to launch by the end of the year. Word processing and spreadsheet software are expected to be the main part of the package.

The ad-supported version will have a store of adverts it will show to people while they put together documents or spreadsheets. The store of ads would be refreshed every time that computer goes online. Microsoft has not said which PC makers it is working with on the project who will pre-install the ad-supported copies of Works.

The software company said the trial would run until mid-2008 and was being run to find out if it can generate enough cash to support such a service. The usual retail price of Works in the US is $39.99 (£20).