The Community Technology Preview can be downloaded at the company's site. Microsoft did not provide details on the new bits in this preview.
Windows Server 2008 is expected to be released by the first quarter of 2008, the same time the software company plans to release Windows Vista SP1.
Last week, Microsoft released a new test build, called Vista SP1 RC Preview, to a group of 15,000 testers with setup and installation changes based on feedback from current beta testers.
The product lineup for Windows Server 2008 was disclosed at IT Forum in Barcelona this week. Microsoft will have eight versions of the server OS, including a Standard version for $999, and an Enterprise version for $3,999 with 25 client-access licenses.
The Viridian hypervisor, also known as Windows Server virtualization, was reintroduced as Hyper-V. The hypervisor will now be offered as a standalone server as well as a feature within Windows Server 2008.
The standalone version of Hyper-V won't be released until sometime in the second half of 2008 and will cost $28 per physical host, Microsoft said.