Microsoft has been ordered to pay out $115m (£64m) to David Colvin, the founder of Z4 Technologies, in a patent dispute over anti-piracy software.
Computer aided design firm Autodesk was also ordered to pay $18m (£10m), following the decision of a US jury.
Colvin took the two firms to the US federal courts in 2004, claiming his patents had been used in Microsoft's Office and Windows XP and Autodesk's AutoCAD products.
Microsoft said it was disappointed with the verdict and could appeal. “We continue to contend that there was no infringement of any kind and that the facts in this case show that Microsoft developed its own product activation technologies well before Z4 Technologies filed for its patent,” a spokesperson said.
Last month, Microsoft was forced to modify its Internet Explorer browser to reduce any liability it may have as a result of a patent dispute with University of California-backed company Eolas Technologies.
Eolas won $500m (£295m) in damages for an alleged patent infringement by Microsoft, over the way IE handles interactive content. The software giant appealed and won the right to a second trial, expected later this year.