Bill Gates has contended that IBM remains Microsoft's biggest threat. Many others would say it's Google or Apple. But don't forget about VMware. The New York Times makes that point today in a profile of the virtualization company, led by former Microsoft executive Paul Maritz.

“After Google, it is the company Microsoft fears most," IDC analyst Gary Chen tells the newspaper.

The story by Steve Lohr quotes people including Maritz and Tod Nielsen -- one of a series of former Microsoft veterans now working for VMware -- and explains the threat it poses to the Redmond company. Virtualization technology from VMware and others let PCs and servers run more than one operating system. Microsoft offers its Hyper-V virtualization technology in conjunction with Windows Server.

From the story:

As 11,000 business partners, developers and customers gather in San Francisco for the start of the company’s VMworld conference on Monday, the strategy under Mr. Maritz is clearly taking shape. In August, the company announced that it planned to pay $420 million to acquire SpringSource, a maker of open-source software development tools, some of which analyze and tweak the performance of applications. Adding such features could allow VMware’s technology to essentially sidestep an operating system like Windows.

“It makes us far less dependent on the operating system to manage the applications,” Mr. Nielsen said.

Microsoft, for its part, isn't ignoring VMware's central role in the virtualization market. The Redmond company is among those exhibiting at VMworld this week.