Here is newest (leaked) build of upcoming Windows 8 a" Build 7959 Milestone 3 but this time in 64bit version (based of Windows 2008 Server R2).
Description: Windows 8 refers to the next version of Microsoft Windows after Windows 7. Scheduled for release around 2012. At the 2011 Consumer Electronics Show in Las Vegas, Microsoft announced that it would be including support for system-on-a-chip (SoC) and mobile ARM processors in its next version of the Windows operating system, which is expected to be called Windows 8.
6.2.7959.0.fbl_srv_wdacxml.110307-1930_amd64fre_server-enterprise_en-us
ISO Size: 3.00 GB (3,229,550,592 bytes)
ISO MD5: 99375D7782027CBF2E70F5D0F8648406
SHA1:48BC9D05BBAC50D7166D60E456088DF78C9F8004
CRC32: 9FD65183