How can I run Windows in a VM using VirtualBox? My image is always permission denied
Most users wishing to do what you want to do purchase VM Fusion or Parallels.

VirtualBox is not really designed for what you are trying to do. Think of what would happen if you were to clone your Windows partition to another entirely different PC. You should not expect Windows to boot because you did not copy any boot code to the new PC. If you were to fix this problem, then you should expect there to be problems with the fact that the hardware peripherals would be different. I suppose you could have generalized Windows before the copy, then installed new drivers after booting Windows on the new PC, but generalization was not meant to be performed after Windows is in use. Anyway, this what you are attempting to do by booting a Boot Camp install of Windows in VirtualBox.

Below are some items you may need to worry about.


You have no boot code. You can use the Windows ISO file to create boot code, but the procedure depends on whether you are going to BIOS or EFI boot.
You have not mentioned if VirtualBox is set to boot the same way. In other words, will you need to BIOS or EFI boot in VirtualBox?
You may need to run "C:\Windows\System32\sysprep" to generalize before booting in VirtualBox. 


I assume you entered the commands given below.

sudo VBoxManage internalcommands createrawvmdk -filename "windows.vmdk" -rawdisk /dev/disk0s3
sudo chown mike:staff windows.vmdk


I would have entered the commands given below.

sudo vboxmanage internalcommands createrawvmdk -filename "windows.vmdk" -rawdisk  /dev/disk0 -partitions 3
sudo  chown  $USER  windows*.vmdk



  Note: You will need to enter the command diskutil unmount disk0s3 immediately before starting the virtual machine.