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I have just installed a 64-bit Ubuntu guest on a quad-core 64-bit Windows XP host in VirtualBox, and I am trying to get the guest to use multiple cores.

However, when I go to Settings -> System -> Processor, the Processor(s) slider bar is greyed out, and when I hover over it the following message appears:

You need hardware virtualization support on your host system to use more tha one virtual CPU.

How do I go about geting this hardware virtualization support?

EDIT: I should mention, my processor is a Core i5 750.

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up vote 4 down vote accepted

Hardware virtualisation is a processor function, and sometimes can be turned on in the bios. Unfortunately, until recently support for vt-x (the 'basic' hardware virtualisation function) was spotty on intel processors (though AMD ones were fine). Look up your processor on intel's webpage, amd's webpage or wikipedia to see if it supports it. If so, check if you can turn it on in the bios settings.

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According to…, my CPU does support hardware virtualization. I will try turning it on in the BIOS. – HighCommander4 May 11 '12 at 0:30

This is something that started to be added to CPUs around 2006. I believe that not every processor supports it but many do. Basically, you'll need to boot into your BIOS and see if you can turn on Virtualization. There is also a Microsoft tool that is supposed to help you determine if your CPU supports it.

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