SEATTLE, US:Microsoft Corp did not infringe a patent held by anti-piracy software maker Uniloc Inc, a federal judge ruled on Tuesday, nullifying an earlier $388 million damages award against Microsoft.

The decision, by U.S. District Judge William Smith, means Microsoft does not need to pay what would have been one of the largest damages awarded in a civil patent case.

"We are pleased that the court has vacated the jury verdict and entered judgment in favor of Microsoft," said Kevin Kutz, a Microsoft spokesman.

A call to Uniloc was not immediately returned.

Uniloc USA and its Singapore-based parent originally filed suit against Microsoft in 2003, claiming that Microsoft infringed its patent with security software it was using to prevent unlicensed use of its Windows XP operating system and parts of its Office suite of products.

After six years of legal wrangling culminated in a trial earlier this year, a jury in the U.S. District Court for the District of Rhode Island found in favor of Uniloc in April, awarding the large damages against Microsoft. Microsoft then appealed the verdict.