On Thursday, Microsoft and individuals representing the U.S. Department of Justice (DOJ) met at Microsoft headquarters in Redmond to begin reviewing Longhorn to make sure it will comply with terms outlined in the final U.S. antitrust judgment against Microsoft.

The compliance-review process is commencing none too soon, some industry-watchers say. Microsoft is set to release a first "technical preview" of the client version of Longhorn in April. And company officials have been touting publicly for a few months some of the new major features — such as the Avalon presentation system and the Indigo communications subsystem — that Microsoft is planning to make the heart of its next major Windows release.

The DOJ and a handful of state governments settled their antitrust case against Microsoft in 2001. As part of the settlement, the plaintiffs and an appointed technical committee have been charged with monitoring Microsoft's compliance with the settlement. Ascertaining that Longhorn, the version of Windows due in 2006, will comply with the settlement terms, is part of the oversight group's charter.

Neither the DOJ nor Microsoft would discuss Thursday's Longhorn meeting.

DOJ officials declined to comment. And a Microsoft spokeswoman reiterated Microsoft's commitment to compliance, but wouldn't talk about Thursday's briefing.

"All development at Microsoft is done with full consideration and understanding of our obligations and commitment under the consent decree and final judgments. We think it's important to be working closely and openly with the DOJ and states early in the Longhorn development process to address any questions and concerns now," said the Microsoft spokeswoman.

Neither the DOJ nor Microsoft would elaborate on potential areas of concern around Longhorn.

If the line of questioning by U.S. District Judge Colleen Kollar-Kotelly during last week's regularly scheduled compliance hearing is any indication, however, Microsoft will likely find itself defending its distribution and integration stances with Longhorn.

According to a source familiar with the exchange between the judge and DOJ attorney Renata Hesse, Kollar-Kotelly was interested in information on OEMs' ability to configure PCs for Windows; how Windows currently handles middleware configuration; and how it exposes application-programming interfaces.

Judge Kollar-Kotelly also asked about Microsoft's strategy for distributing various system-software components, specifically whether Microsoft is delivering them separately from Windows or makes them available only as an integrated part of Windows, said the source.

Microsoft is set to make available a "preview" release of Longhorn at the Windows Hardware Engineering Conference in late April. Company officials have said Microsoft is planning to deliver a first Longhorn beta release this year.

Microsoft is making two of the main pieces of Longhorn — Indigo and Avalon — available on Windows XP and Windows Server 2003, in addition to integrating them into Longhorn. Microsoft's decision to "modularize" these elements has led some company watchers to speculate that Microsoft is hedging its bets, in case it is forced to cut these systems from Longhorn as a result of legal proceedings.

Microsoft officials have denied that legal concerns are behind the decision to modularize Longhorn.

Microsoft recently was required as part of a separate antitrust case against it in Europe to begin shipping a version of Windows XP that does not include Windows Media Player as part of it. Microsoft is planning to rename that version of Windows, which it originally christened "Windows XP Reduced Media Edition," in order to address the European Commission's concerns that the Redmond software company was not complying fully with the remedies ordered by the Commission.

Microsoft and DOJ/state representatives are expected to hold additional briefings later this year on Longhorn's compliance with the final antitrust judgment.