Fixing the “Your PC needs to restart” error in Windows 8.1 in VirtualBoxJust a quick tip for people out there trying out Windows 8.1 in Oracle VirtualBox. If you’re experiencing the following error when you try to boot from the ISO:

Your PC needs to restart.

Please hold down the power button.

Error code: 0x000000C4

Parameters:

0×0000000000000091

0x000000000000000F

0xFFFFF801E5962A80

0×0000000000000000

Here’s the solution. Open a command prompt in the directory in which you installed VirtualBox and run the following command:

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

Where [vmname] is the name of your virtual machine, which can be discovered with:

VBoxManage.exe list vms

Don’t forget to wrap your VM name in quotes if it contains spaces.

This command enables the CMPXCHG16B CPU instruction. You can find more info on the Wikipedia article on X86-64.