If you wanted to start a VirtualBox VM headless (no UI) in the past, you needed additional tools.  I always found this to be a bit of a pain that VirtualBox didn't support this 'out of the box'.  Thankfully Version 5.0 has been recently released and it will finally handle this for you. Yay!

There is now a command line option for starting your VMs without having to open the UI.  This means we can add it to our windows startup and our VM can start with windows. To test this out, you need to know 2 things:

1. Location of your VirtualBox install.
2. The name of the VM you want to start.

Create a shortcut to start the VM headless

Right click your desktop and 'create a new shortcut'.  For the path of your shortcut you want to Browse to the VirtualBox install location and select VBoxManage.exe, Save and then right click the new shortcut to edit the properties.  From here we just need to add some extra arguments to the Target: startvm "MyVMName" --type headless

In my case the VM was Named "Ubuntu14" so the target ended up looking like this:

"C:\Program Files\Oracle\VirtualBox\VBoxManage.exe" startvm "Ubuntu14" --type headless

To test, simply double click your new shortcut. If all goes well the VM should start minus the UI.

Getting it start with windows 10

This probably works with previous versions of Windows too.  Press Windows Key + R to open the run dialog.  Then type:

This will open your startup folder, simply drag your shortcut created earlier into this folder.  Job done! Your VM will now start with Windows on startup.