I have installed Windows Server 2008R2 and now trying to install multiple Windows Server 2008R2 as guest. My CPU is Intel Core 2 Quad Q8400 @ 2.66GHz on Asus P5P41T-LE mainboard. First I have to tell there is no place in BIOS to enable Intel VT-x. Intel web site says this CPU supports VT-x. When installing guests, VirtualBox says:

attempting to load a 64-bit application however this cpu is not compatible with 64-bit mode

But Hyper-V can load 64 bit guest with no problem. I have tested my CPU with Securable tool. It says my CPU does not support VT-x. The question is WTF is happening? Are there two editions of Q8400 with/without VT-x?

  • The 8400 should have VT-x but it is missing VT-d. So it should be working perfectly fine. Have you stopped Hyper-V and it's related services before starting VirtualBox? Running multiple VM softwares at once can cause bad things to happen (usually instability of the host) – Justin Nov 27 '12 at 12:24
  • Yes I have checked VirtualBox before starting Hyper-V services. – Majid Azimi Nov 27 '12 at 12:56
  • This sounds like a problem with Virtual Box does VMWare have this problem? This will require running the Hyper-V Services. – Ramhound Nov 27 '12 at 13:09

I just had the same problem with Hyper-V being able to host 64bit systems, while on the same machine VirtualBox wasn't. The issue is that the Hyper-V service occupies VT-X right after startup, hence no other service (like VirtualBox) can claim it.

The only way I found to resolve the issue was by completely removing the entire Hyper-V feature through the windows feature settings an rebooting. After that VirtualBox was able to host 64bit systems.

See see this answer on how to turn Hyper-V on and off, without having to remove the feature completely.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.