The editions -- Foundation, Essentials, Standard and Datacenter -- contrast with the twelve editions for Server 2008 R2. For companies with fewer than 250 computers, pricing ranges from $425 to $4,800, and larger enterprises will be eligible for volume discounts.

'Excellent Economics'

Windows 8 has similarly undergone a versioning diet, going from at least five editions for previous Windows operating systems to three retail versions -- Windows 8, Windows 8 Pro, and Windows 8 RT.

We asked Charles King, an analyst with Pund-IT, if the simplification of Server edition options will matter much for potential buyers.

He said it could, and that, since Windows Server is the "dominant OS in data centers looking for standardized, out-of-the-box usage," this makes the choices fairly clear. King said data centers that wanted a highly customizable server still generally preferred Linux.

Microsoft said all the new editions "deliver excellent economics and ROI," and all four versions provide some level of support for cloud -based computing.

Datacenter is designed primarily for highly virtualized private and hybrid cloud environments, and features full Windows Server functionality with unlimited virtual instances. Standard is targeted at low-density or non-virtualized environments, and also has the full Windows functionality offered in Datacenter but with only two virtual instances.

Microsoft pointed out that the Datacenter edition, with unlimited virtualization rights, provides the "benefits of cloud-level scale with predictable, lower costs." The company also noted that Standard edition has the same enterprise -level functions as the Datacenter except for virtualization.

Choice by 'Virtualization Strategy'

The choice between the two editions, the company said, should be based "solely on your virtualization strategy." If a customer might need to expand virtualization capacity later, Microsoft said, additional Standard edition licenses can be purchased, or, if the Standard license has Software Assurance, a Step-Up can be purchased to migrate to Datacenter.

Single licenses for either Standard or Datacenter include up to two physical processors. Standard's license includes two processors and two virtual machines, while Datacenter's includes an unlimited number of virtual machines on up to two processors.

Features that were formerly available only in premium editions are now included in Standard. These include Windows Server fail-over clustering, BranchCache hosted cache server, Active Directory federated services, additional Active Directory certificate services capabilities, distributed file services support for more than one DFS root, and DFS-R cross-file replication.

For small-business environments, the Essentials edition provides a simpler interface, no virtualization rights, and pre-configured connectivity to cloud-based services.

And Foundation, intended only for OEMs, is the general purpose, economical server with no virtualization rights and a limit of 15 users per account.