I have been trying to download and run Back track Linux 5 r3 on my windows 8.1 (AMD Quad-Core processor, 64bit Intel.) using Virtual Box. It kept giving me the error "This Kernel requires an x86-64 bit cpu but only detected an i686 cpu so I downgraded to 4.2 Virtual Box. That solved the problem but now I keep getting an error when I run Virtual Box linux with Ubuntu 64 bit "VT-x/AMD-v hardware acceleration is enabled but not operational. Your 64-bit guest will fail to detect a 64-bit cpu and will fail to boot. Please ensure that you have enabled VT-x/AMD-v properly in the bios of your host computer." I have searched and digged through the internet and found nothing useful to my predicament. How can I enable VT-x/AMD-v in my windows 8.1 bios so I can run Back Track Linux properly? Ive looked through my bios and found nothing relevant to Virtualization or VT-x/AMD-v so I came here. Thanks :D
Apparently the support for enabling AMD visualization (SVM) is hidden in the advanced bios features. This thread explains how to expose the hidden "advanced features" in your bios.
This video shows the hidden advanced features in the Acer Aspire V5-122p bios, including AMD-Virtualization Technology @1:48.
Sometimes Windows 8.1 uses Hyper-V itself by default for some reasons, so VirtualBox is not capable to use it too. You can force Windows 8.1 not to use Hyper-V. Just run 'cmd.exe' with administrator rights and type:
bcdedit /set hypervisorlaunchtype off
But it may cause some lags in work of Windows UI. So, to turn it back, type:
bcdedit /set hypervisorlaunchtype on
Don't forget to restart your computer after these actions.
来源：https://stackoverflow.com/questions/20770494/how-to-enable-vt-x-amd-v-in-aspire-v5-122p-bios