The follow-up to Windows Vista - Windows 7 - is to be probed by technical advisers to the antitrust regulators who monitor Microsoft's business practices in the US.

Though few details are known about Windows 7, and those that are available rely on shaky evidence, the three-person panel of computer experts that works for state antitrust officials has a copy of the operating system, according to the status report filed late last month with US District Judge Colleen Kollar-Kotelly.

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"In addition, the TC [Technical Committee] has begun to review Windows 7 itself. Microsoft recently supplied the TC with a build of Windows 7, and is discussing TC testing going forward," the report said. "The TC will conduct middleware-related tests on future builds of Windows 7."

Microsoft has been under the eye of regulators since it struck a deal in 2002 that required the company to document communication protocols. The decree also set up the TC and forced Microsoft and state and federal antitrust officials to deliver regular reports to Kollar-Kotelly.

Although the decree was originally set to expire in early November 2007, several states objected, and after months of legal back-and-forth between the states and Microsoft, in January Kollar-Kotelly extended the decree's rules and enforcement policies by another two years to November 2009.

"The provisions of the final judgements have not yet had the chance to operate together as the comprehensive remedy the court and the parties envisioned when the final judgments were entered," she said then.

Parts of the 2002 decree requires that for any new feature added to Windows which meets the definition of 'Microsoft middleware product', Microsoft must help rivals integrate their similar software with Windows. Last year, Google argued that Windows Vista's desktop search was a new feature - not an extension of the search in Windows XP - thus making it middleware, meaning Microsoft should be forced to open Vista to other search providers.

Microsoft conceded the point before Kollar-Kotelly could rule; Vista SP1, which rolls out to the general user population this month, sports changes that allow users to select non-Microsoft search engines to power Vista's desktop search.

That example is important, since it points to the scrutiny Windows 7 will be subjected to. "Microsoft's learned that this oversight is not going away very quickly, and that they have to deal with it proactively," said Michael Gartenberg, an analyst with JupiterResearch. "Its challenge for Windows 7 will be how can it continue to add features that consumers will want that also don't run afoul of regulators?"

Microsoft has talked up a 2010 release for Windows 7, putting the ship date after the expiration of the degree. But that may be moot, since the bulk of the operating system's development will take place during oversight. In any case, Kollar-Kotelly made it clear that there's nothing stopping her from extending the decree again. "The door likewise remains open for the court to reassess the need for continued oversight as the expiration of the final judgments in November 2009 approaches," she said in her January ruling.

Almost certainly, Windows 7 will have to toe the line from start to finish. That may, said Gartenberg, make Microsoft hesitate to add much new to Vista's follow-up. "There are any number of things that it might want to add to compete with Apple and Linux," said Gartenberg. "Microsoft has to announce features, but not in a way that locks out OEMs from making changes. It has to provide some degree of open access to Windows 7."

That push and pull - push for more features to entice users to upgrade from Vista or XP, pull back to ward off possible antitrust conflicts with the regulators, the TC and Kollar-Kotelly - is unique to Microsoft, said Gartenberg.

"Is Microsoft at a disadvantage here? Absolutely. No one else has this degree of oversight. No one's telling Apple, for example, that it can't include iTunes with Mac OS X."

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