U.S. anti-trust enforcers have started to track Microsoft's development work on Longhorn, the successor to Windows XP, in a move to ensure that the vendor won't violate the final judgment in the government's anti-trust case.

The Department of Justice and several U.S. states involved in the case are particularly interested in any changes that Microsoft might make in Longhorn related to default settings and "middleware," or applications associated with the operating system, such as Web browser and media player software, according to a legal filing on Friday.

As part of the final judgment, Microsoft has to make it easy for users and PC vendors to remove access to Microsoft middleware products and select competing products instead. Additionally, Windows can't be programmed to automatically change the configuration of icons, shortcuts or menu entries installed by a PC vendor.

"Early attention to these issues will enable plaintiffs and Microsoft to address any potential concerns in a timely matter, before the final structure of the product is locked into place," the filing reads.

The filing in U.S. District Court for the District of Columbia is a joint status report on Microsoft's adherence to the final judgment in the Justice Department's anti-trust case against Microsoft, made in 2002. The judgment was entered after Microsoft settled the case with the  Justice Department and several U.S. states in 2001.

Microsoft has provided the anti-trust authorities with information on the development of Longhorn and discussions about the future operating system release have begun, according to the filing. Longhorn is expected to be released in 2006, and a first beta of the product is slated for release in early 2005, Microsoft has said.

A technical committee for the  Justice Department and the states is also testing the upcoming Service Pack 2 for Windows XP for compliance with the final judgment. The work includes running hundreds of tests to check the behavior of Windows in relation to third-party middleware products. Similar tests will be done with Longhorn, according to the filing.

The joint status report also discusses continuing issues regarding Microsoft's compliance with the final judgment in the anti-trust case, including the Microsoft Communications Protocol Program (MCPP) and Microsoft's licensing terms for PC vendors.

The IDG News Service is a Network World affiliate.