The office ruled that the term - which Microsoft adopted for its successful operating system in 1983 - has a generic meaning in the industry and that it was in use long before the firm tried to copyright it.
'Windows', now commonly understood to mean Microsoft's system, also describes overlapping rectangular displays that allow computer users to bring more than one program to the screen at a time.
Microsoft, which says it will appeal against the ruling, argues that the loss of the trademark creates the danger that consumers will be sold inferior products and allows competitors to cash in on its expensive marketing efforts.
Windows makes IBM-compatible computers as easy to use as those produced by Apple. Most of the software industry now tailors its programs to the Windows systems, and Microsoft charges no royalty for the use of the name. But it does require licences and set rules for 'proper use' of the logo.Reuse content