Microsoft (MSFT) announced its annual spring cleaning of top executives late Thursday. Although the reorganization constitutes only a minor reshuffle, the most telling change is that a separate group within the company - on par with the existing Windows and Office groups - is now devoted to building a platform for Web services.

The reorganization also affirms the central role of Rick Belluzzo, who was appointed president and COO in February. The one exec to get a significant promotion is Yusuf Mehdi, who now takes charge of MSN.

In a statement, CEO Steve Ballmer said the goal of the changes is "to ensure that Microsoft's flagship products, Windows and Office, continue to provide value and relevance to customers, and that Microsoft builds a software services platform."

The importance Microsoft places on its move to the Web is apparent in the new structure. Everyone at the company has by now had it drilled into their brain that the company's future depends on a project dubbed .Net, which seeks to shift its software from the desktop onto the Web.

On March 19, Chairman Bill Gates announced a major step in implementing .Net: a plan, code-named HailStorm, to build a platform for Web services. HailStorm includes the development of a set of basic Web services that third-party programmers will be able to use as "building blocks" to plug into Internet applications. It also entails the building of physical data centers that can host the data of millions of users. With this reorg, Group VP Bob Muglia's division - which is building the HailStorm Web services platform - becomes a separate group within the company. That puts Muglia at the level of Jim Allchin, who leads the Windows platform group, and of Jeff Raikes, who leads the group that runs Office.

Rick Belluzzo retains the sweeping role that was assigned to him in February. He's in charge of sales and marketing, financial operations, business development, MSN and the development of the Xbox game console.

Mehdi, however, will take over the day-to-day running of MSN, reporting to Belluzzo. Mehdi, who has been at Microsoft for eight years, made his reputation in the mid-1990s when he led the aggressive introduction of the Internet Explorer Web browser, which came from nowhere to eclipse Netscape's browser. That campaign was central to the Department of Justice lawsuit against Microsoft, which is now on appeal.

Microsoft's top management team is now aligned toward one clear goal: consolidating its desktop dominance while transitioning onto the Internet.