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I'm using VirtualBox-4.3.6-91406-Win on Windows 7 x64 with an AMD 64-bit processor. The virtualbox installation is also a 64-bit install. I've been able to install Win Server 2008. When I try to install ubuntu-13.10-desktop-amd64.iso in Virtualbox, I get this msg:
This kernel requires an x86-64 CPU, nut only detected an i686 CPU. Unable to boot - please use a kernel appropriate for your CPU.
I'm using an AMD Phenom II X2 555 processor. It sounds like the .iso file may be corrupt? Any ideas/thoughts would be greatly appreciated.