Bill Gates has offered his testimony on Monday in the $1 billion antitrust lawsuit filed by the former owner of WordPerfect.

Gates said that the release of Windows 95 was a very challenging task for the company and several last minute pre-launch changes were made to the platform, which meant that the support for a rival software maker's word processor was dropped.

"We worked super hard. It was the most challenging, trying project we had ever done," the Microsoft co-founder said.

Lawyers representing Microsoft presented their case in the trial and Gates was the first witness to testify on Monday. He will continue with his testimony on Tuesday morning.

The trail has been going on for in federal court in Salt Lake City for about a month.

Novell Inc had filed a case against Microsoft in 2004 arguing that the software major violated US antitrust laws through its arrangements with other software makers during the time of the launch of Windows 95. Novell said that it was forced to sell WordPerfect for a loss of $1.2 billion. Novell now operates as a wholly owned subsidiary of The Attachmate Group.

Gates pointed that Novell was not capable for delivering a Windows 95 compatible WordPerfect program within the time frame. On the other hand, the company's own Word program was better in performance. He also said that the company decided t drop the technical features that supported WordPerfect due to concerns over it causing system crashes.

"We were making trade-offs. We thought everybody would have a personal computer on every desk and in every home. We wanted to be there and be the first," Gates said.