Trying to boot Windows 8.1 or Windows server 2012, either a previously installed VM or booting from CS/ISO on virtualbox gives Error code: 0x000000C4.
This solution fixed the problem for me:
You need to set a parameter in virtualbox to enable a certain CPU instruction. [vmname] should be replaced with the name of the affected VM without square brackets.
"c:\Program Files\Oracle\VirtualBox\VBoxManage.exe" setextradata [vmname] VBoxInternal/CPUM/CMPXCHG16B 1
VBoxManage setextradata [vmname] VBoxInternal/CPUM/CMPXCHG16B 1
I also had the same issue, and it's also possible to set
"C:\Program Files\Oracle\VirtualBox\VBoxManage" setextradata global VBoxInternal/CPUM/CMPXCHG16B 1
However I also had to go into the BIOS and change the
Memory Protection setting from
Enabled before the issue went away.