I installed Windows 2008R2 Enterprise on a Intel DX79SI-System with Core i7-3930K and 64 GB DDR3 RAM. The System runs without problems.
But when i identify the processor with the intel processor identify tool, it says, that the processor have no Intel virtualisation technologie and no Intel VT-x ( In the Bios both VT-Switchs are enabled)- So virtualbox can only emulate 32bit Windows...
What´s the reason for the missing point of processor indentifier test?
Hmm, I've got the same mobo and CPU, a bit less RAM, on Windows 8 (x64) and it reports no intel virtualisation technology, so its not your OS.