Full screen not working properly

[Thomasio]

Not sure if I just haven´t found the settings for this, or it doesn´t exist.
In short I would love to have an option like "allow guest to change monitor resolution".

Problem:
When running a VM in full screen mode and then I change the resolution within the virtual machine, instead of changing the screen resolution VirtualBox displays a black frame, where the actual desktop of the VM is displayed in the center.
On a 26" screen @ 1920x1200 a VM @ 640x480 (i.e. to run some games that do not support any other resolution) is not really usable.

[Perryg]

To run games in full screen at the lower resolution you will need to set the host to the lower resolution and the run the guest in full screen.

[Thomasio]

I figured that as a workaround, but obviously it messes up the desktop of the host, like positions of icons and initial positions of windows.
Not really a final solution, but ok, for now it will do.
Thanks for the reply.