You may see this message while trying to run VirtualBox on Windows 10: raw-mode unavailable courtesy of Hyper-V. To solve this problem follow these steps:
Open the command prompt as an Administrator.
Run the command with no argument: bcdedit.
You will see that the property hypervisorlaunchtype is set Auto by default.
Disable Hyper-V by running the command: bcdedit /set hypervisorlaunchtype off
Restart your PC
Launch VirtualBox and start your OS image
Hope this helps.