Microsoft has been ordered to pay $388 million in compensation after a court found it had infringed a patent in its anti-piracy measures.

Uniloc alleged before the Federal Court in Rhode Island that Microsoft used its patented technology as part of Microsoft’s product activation methods. The court found that Microsoft had infringed the patent in Windows XP, Office XP and Windows 2003.

Microsoft spokesperson David Bowermaster said that Microsoft would appeal the ruling. “We believe that we do not infringe, that the patent is invalid and that this award of damages is legally and factually unsupported,” he said. “We will ask the court to overturn the verdict.”