In addition to Windows 7 Beta Build 7000.0.081212.1400 (download link), Microsoft has also made available the checked builds for both the client and server flavors of the operating system. However, although meant for testing, the checked builds of Windows 7 client Beta and Windows Server 2008 R2 Beta (Windows 7 Server Beta) (download link) are designed with a specific target group in mind: device driver developers.
The developer releases are only available through Microsoft Connect. The following Connect ID WIN7-3HQW-RF74 along with a Windows Live ID permits access to the downloads. Microsoft is offering 7000.0.081212-1400_server_unstaged_en-us-GB1SXCHK_EN_DVD.iso; 7000.0.081212-1400_client_unstaged_en-us-GB1CXCHK_EN_DVD.iso; 7000.0.081212-1400_server_unstaged_en-us-GB1SIAiCHK_EN_DVD.iso and 7000.0.081212-1400_client_unstaged_en-us-GB1CCHK_EN_DVD.iso.