In a sign that legal troubles continue to hound

Microsoft

(MSFT) - Get Report

, a federal jury in Chicago on Monday found the software goliath infringed on the patent of the University of California and a small start-up and awarded them $521 million.

Twelve jurors found that the Redmond, Wash., software company infringed on the interactive Web-browsing technology of Chicago-based Eolas Technologies and the university, according to wire reports.

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The suit, which dates back to February 1999, charged that Microsoft infringed on Eolas' patent on Web-browser technology that makes "plug-ins" and "applets" possible.

The award was based on the jury's calculation that $1.47 per unit of royalties for 354 million copies of Windows sold from the time the patent was granted in 1998 until September 2001, according to news reports.

Microsoft, which has more than $49 billion in cash and short-term investments on its books, plans to appeal the jury finding. The company has cited outstanding legal issues as the obstacle to spending its cash hoard.

Calling the verdict "disappointing," Microsoft noted that the award is less than the approximately $1.2 billion Eolas was seeking in the trial. "It is important to note that the court has already rejected claims that there was any willful infringement," the company added in a statement. "We believe the evidence will ultimately show that there was no infringement of any kind, and that the accused feature in our browser technology was developed by our own engineers based on pre-existing Microsoft technology."

Eolas, which is privately held, was founded in 1994 by Dr. Michael Doyle and his research group as a spinoff from the University of California to create and market new technologies and products that make the Web more interactive.

Shares of Microsoft closed up 3 cents, or 0.1%, at $25.61. Shares inched up to $25.64 in after-hours trading.