Last year, Microsoft faced complaints from rivals about the way the pending Vista operating system handled search, antivirus security and certain document formats, among other things.

European Union antitrust chief Neelie Kroes told Microsoft in March 2006 that she, too, was worried features in Vista could limit customers' choices and competitors' ability to develop programs that run smoothly on Windows.

Ahead of Vista's November 2006 launch to businesses, Microsoft said it made changes that solved EU and competitors' concerns. Regulators, however, did not give Microsoft the green light, saying it should know how comply with antitrust law.

Since then, the EU hasn't made any public moves to re-examine Vista, but neither has it given Microsoft the all-clear. Kroes dodged questions Monday about whether regulators would revisit Vista concerns, saying, "if it is not in line with our policy, then we will act."

Analysts were split on whether Microsoft's Vista changes are enough to ward off further EU scrutiny.

Matt Rosoff, an analyst at the independent group Directions on Microsoft, said Vista clearly reflects the European Commission's antitrust verdict against Microsoft three ago.

"Without the 2004 decision having been in place, they might have been more aggressive about bundling features, like Web search," Rosoff said. "I think they've been pretty careful about what they're putting into Vista."

Microsoft's shift may be more evident in future iterations of the operating system, Rosoff said. He predicted Windows updates in the future might focus on behind-the-scenes technology, with new or updated consumer programs being offered separately, like Microsoft new "beta" versions of some Windows Live programs.

"This is actually a good thing for Microsoft," Rosoff said. "In the old days, they could rely on Windows to promote products. Now, each one has to compete on its own merits."

But Michael Silver, an analyst for researchers Gartner Inc., said Vista isn't out of danger yet.

"Microsoft did a number of things to pre-emptively repair things in Vista that they thought might come up," Silver said, but "the EU could demand certain things that are beyond what Microsoft would willingly do."

For example, he said, regulators could tell Microsoft to hand over proprietary Vista technology to competitors, as it has done with Microsoft's server technology.

"The European Union's definition of what Microsoft is doing to extend the monopoly is so broad, it's easy to think of things that the EU could ask them to do," Silver said.

Microsoft's antitrust problems have, so far, been tied primarily to its operating system and server software divisions, but the company faces competition on many more fronts today, from Web search and services to consumer electronics.

Some of Microsoft's rivals indicated Monday that they will continue to hammer on antitrust issues not only with Vista, but in other business areas as well.

Thomas Vinje, a lawyer for the European Committee for Interoperable Systems, which represents IBM Corp., Sun Microsystems Inc. and others, said last year's changes to Vista were "low-hanging fruit."

Vinje and colleague Dieter Paemen ticked off a list of things that still trouble ECIS, some related to Vista but many to the way desktop programs are tied to Microsoft's server products, and to Microsoft's moves in the area of rich Web application development.

In the U.S., Microsoft is also fending off Vista-specific pressure. Several states asked the Justice Department to extend oversight of Microsoft's business practices -- part of a 2001 antitrust settlement with federal and state governments -- to afford more time to examine Vista.

Kroes plans to discuss the Microsoft ruling with U.S. authorities when she visits New York at the end of the month. But she would not speculate how the court decision would influence other high-profile monopoly abuse cases against Intel Corp. and Rambus Inc.

"Let me be clear -- there is one company that will have to change its illegal behavior as a result of this ruling: Microsoft," she said.

AP Business Writer Aoife White contributed to this report from Brussels, Belgium.