Microsoft announced this mornning the official release of its ESXi equivalent called Hyper-V Server. While its installation package doesn't arrive in as small a size as ESXi (1G vs 32M), its feature set could be considered roughly equivalent. A free download, this solution brings Microsoft's offerings in the virtualization space to parity with VMware.

From the press release:

"Customers have been telling us that virtualization is a top priority, but they continue to face multiple barriers to adoption, such as costs, complex tools and limited certified virtualization professionals," said Zane Adam, senior director of virtualization strategy at Microsoft. "In response, Microsoft is breaking down these barriers through new training programs and services, interoperability, centralized management tools, and a broad partner ecosystem built around the Windows hypervisor to help make virtualization ubiquitous. Microsoft's new virtualization products will help customers get virtual and manage their virtual and physical assets across datacenters and desktops."

Get your copy today at: http://www.microsoft.com/servers/hyper-v-server/default.mspx