Microsoft was slapped with a $388m patent infringement fine yesterday, following a lengthy legal row with anti-piracy software vendor Uniloc.
Redmond said it was disappointed with the verdict and added it planned to appeal.
The long-running lawsuit was originally brought by Uniloc USA and its Singapore-based parent company in 2003, in which the firm alleged Microsoft had infringed its patented technology for its software activation methods.
The trial began on 23 March and the jury in the case reached its verdict in federal court in Rhode Island on Wednesday.
"We believe that we do not infringe, that the patent is invalid and that this award of damages is legally and factually unsupported," a Microsoft spokesman told Reuters. "We will ask the court to overturn the verdict."
It is understood that the damages award against Microsoft in the infringement case is one of the largest on record in legal disputes involving patents. ®