VirtualBox 4.3 is much more strict regarding the distinction between 32 and 64-bit guests. This will then expose 64-bit CPU features to the guest. Now as for your real problem, not being able to load 64-bit guests change the guest-OS type to 64-bit or use this command: The Intel code is what was buggy which has been fixed in trunk and will be available in the next maintenance release. If (!(u64FeatMsr & MSR_K8_VM_CR_SVM_DISABLE)) Since the log file shows AMD-V is enabled, perhaps it is a typo/bug in the Support driver code that differs from the VM-initialization code (which was what it was for VT-x) but I checke and as far as I can see that is not the case. AMD-V cannot be enabled which is what VirtualBox will report as 'VERR_SVM_DISABLED'. If the BIOS sets this bit, then according to the AMD-spec. Particularly, bit 4 of that MSR must be clear (zero) for AMD-V to be enabled. On AMD CPUs, the MSR in question would be 0xc0010114. VM VirtualBox On newest version, no more problems with VHDs, only the Guest-Additions doesn't works on Windows 8.1.

portable version on or from directly download at Oracle. That forum thread is only talking about VT-x and not AMD-V. For Windows 8 and Windows 8.1 is Oracle VM VirtualBox a great software Use the portable version of Virtual-Box for install.

Virtualbox download for windows 8.1