I have just started using VirtualBox on a 64bit version of Windows 7. So far it has been running a Ubuntu for a few weeks with no problems.

Today I tried to get OSX to work. I created a virtual machine according to this guide but so far, regardless of whether the OSX DVD is mounted or not, the machine immediately crashes with the following error:

Failed to open a session for the virtual machine OSX

Unknown error creating VM

After googling this message, it seems this is usually caused by the host machine not supporting virtualization properly. However, I know this cannot be the case because it runs Ubuntu fine.

What is going on?

  • Do you have any other virtualization software running ? – Sathyajith Bhat Dec 7 '10 at 16:00
  • Which version of Virtual Box are you using? – Madison S Dec 7 '10 at 16:08

Unlike Ubuntu guest, OS X requires VT-x instructions to be enabled. Check in your BIOS is VT-x ( aka hardware virtualization) is enabled.

  • Ah thanks. I thought they both required it. I checked in my BIOS and it was indeed disabled. It now works. Thanks again! – Rupert Madden-Abbott Dec 7 '10 at 16:08
  • you're welcome Rupert! I faced the same problem when I was trying out OS X in VirtaulBox – Sathyajith Bhat Dec 7 '10 at 16:10

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