Fixing Screen Resolution in VirtualBox

Sometimes a virtual pc in VirtualBox will refuse to take up the whole screen.  Even in Full-Screen mode, it will insist on showing things in a 1024x768 resolution.   To fix this, you need to open a command prompt and run one of the following from c:\Program Files\Oracle\VirtualBox .   This was taken from section 9.8.2 of the VirtualBox manual

VBoxManage setextradata global GUI/MaxGuestResolution any

will remove all limits on guest resolutions.

VBoxManage setextradata global GUI/MaxGuestResolution >width,height<

manually specifies a maximum resolution.

VBoxManage setextradata global GUI/MaxGuestResolution auto

restores the default settings. Note that these settings apply globally to all guest systems, not just to a single machine.