Microsoft's quest for another trial in a patent-infringement case it lost has resulted in a bigger fine for the software company.

A judge in a US District Court in Eastern Texas slapped an additional $25m (about £13m) in 'enhanced damages' on Microsoft for 'litigation misconduct' in a patent case z4 Technologies brought against the software vendor and Autodesk in September 2004.

In his ruling, US District Judge Leonard Davis said that Microsoft tried to have z4's patents declared unenforceable even as it continued to willfully infringe on those patents and withheld evidence of its actions. He ruled that this misconduct merits adding to the amount of damages Microsoft must pay z4 in the case.

Davis also denied motions by both Microsoft and Autodesk to schedule a new trial after a ruling in April that they must pay z4 millions of dollars for infringing on two of the company's patents.

The Texas court awarded z4, a private company founded by David Colvin and based in Commerce Township, Michigan, $115m (£61m) from Microsoft and $18m (£9.5m) from Autodesk to settle a patent-infringement suit.

In addition to the added $25m fine levied against Microsoft, the company also must pay z4 $1.98m (£1m) in lawyer's fees, according to court documents. A judge also ordered Autodesk to pay $322,000 (£170,000) in attorney's fees to z4 and also upheld the company's original fine.

The verdict in the case in April found that both Microsoft and Autodesk infringed on US Patent Number 6,044,471 and US Patent Number 6,785,825, both held by z4. The patents are for product-activation technology aimed at preventing unauthorised use or piracy of software.

z4 develops digital rights management technology. The company could not be reached immediately for comment yesterday.

Both Autodesk and Microsoft continue to contend that neither company infringed on z4's patents. In an emailed statement on yesterday, Autodesk spokeswoman Caroline Kawashima said the company is 'very disappointed' and plans to appeal the decision.

"We believe that the facts in this case clearly show that Autodesk and others developed their own product activation technologies well before z4 Technologies claims to have created this technology," she said.

In a statement from its public relations firm, Microsoft echoed Kawashima's statements and said it also plans to appeal the court's decision.