I really dunno whats up with my machine - but I was getting Error Code 0x0000005D when trying to boot from the iso.
So I'm really writing this for my own future reference.
So fixing that is actually really easy. Do the following with VirtualBox closed.
- Navigate to the Virtualbox folder in Program Files. It should be something like C:\Program Files\Oracle\VirtualBox
- Hold down shift and right-click somewhere in the window - not on a file.
- Select Open command window here from the right-click menu.
Copy and past the following into the Command Prompt window:
VBoxManage setextradata [vmname] VBoxInternal/CPUM/CMPXCHG16B 1
Replace [vmname] with the name of your VM. If the name has spaces, you'll need to put double quotes around the name.
- Press Enter.
And you're done. Enjoy Windows 10!