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Problem : Got an error, while trying to install Windows 8.1 on Oracle VM VirtualBox Manager.


Your PC needs to restart.

Environment :
Host OS : Windows 7 Professional.
Oracle VM VirtualBox Manager v4.1.6 r74713
Guest OS : Windows 8.1 Professional.

Analysis : Finding solution for this problem, I found that I need to enable VT-x/AMD-V option in BIOS. I did the same but in vain. Further searching continued. Next finding was that I need to enable "No execute Memory Protection" or "Execute Disabled Bit" under CPU configuration in BIOS again. But this time I couldn't find this option.

I did also try firing following command in VirtualBox installation directory. But even this didn't help me.

VBoxManage.exe setextradata [vmname] VBoxInternal/CPUM/CMPXCHG16B 1

Where vmname can be found by following command
VBoxManage.exe list vms


So up till now nothing worked! :(
But finally got it Solved.
I found that the version of Oracle VirtualBox I am using does not have support for Windows 8.1.
I downloaded the latest(v4.3.6 r91406)  version and selected version in guest OS setting as follows

VirtualBox Settings

Note : I also enabled PAE/NX option under processor tab of guest OS settings.
Did it work for you?