Software giant Microsoft has been ordered by a US court to pay out more than half a billion dollars for breaching a patent with its Internet Explorer web browser.
A Chicago jury found that the part of Explorer designed to enable extra functions through "plug-ins" - add-on programs - infringed patents held by a small Chicago company and the University of California.
The jury ruled that the two should be paid $1.47 for every copy of Windows, Microsoft's computer operating system, sold between 1997 and 2001 - which makes the total fine $520.6m (£324m).
Microsoft said it was disappointed by the decision, and that it planned to appeal.
Windows - and Microsoft's decision to package Explorer into it for free - has been at the centre of a succession of battles over whether Microsoft has a monopoly in software and whether it has abused its position.
Last year, the US Department of Justice settled a long-running case which had found Microsoft to have done just that, in the process massively reducing the stringent penalties a trial judge had decided to impose.
That case revolved around the alleged "bundling" of Explorer so as to beat Netscape's Navigator browser, then the market leader but now little more than an also-ran.
Eolas, the Chicago company, said in court that the functions described in its patent had been incorporated into Explorer without its permission.
That, Eolas said, was a key part of Microsoft's ability to take on Navigator.
Although the US anti-trust case is largely wrapped up, the European Commission is still pushing forward with its own investigation.
A week ago it said it had plentiful evidence that Microsoft was still abusing its monopoly position despite losing the US Government court case, applying its muscle to the audio-video and server markets as well.