In a point-by-point argument contained in , VMware claimed that Microsoft is "leveraging its ownership of the market-leading operating system" to restrict customer choice. VMware also detailed "tactics" that it said are an "attempt to force" users to buy bundles of Microsoft products.

Srinivas Krishnamurti, VMware's director of product management and market development, said in an interview that the EMC Corp. subsidiary is trying to bring its concerns to the attention of customers in the hope that they will seek changes from Microsoft.

"We want to highlight the terms that are not in the best interest of customers," Krishnamurti said. "The hope is that the industry evolves and provides a much more open and interoperable environment in the virtualization landscape."

VMware, by its own estimate, controls more than 80 percent of the virtualization market. And the company has been so confident of its market position that at its annual VMworld user conference last fall, it allowed competitors, including Microsoft, to on the trade show floor. That's what makes VMware's new posting so striking.

VMware's white paper points to seven specific issues, including customer support. For instance, VMware asserted that Microsoft requires VMware users to have its Premier-level support if they run into an issue with Windows or other Microsoft products in a virtualized environment. Otherwise, Microsoft may request that a user first replicate the problem on a physical machine. Krishnamurti said there is no technical reason for that requirement.