problem with screen resolution

This should resolve your resolution issue on Virtual Box although if you need further help do not hesitate to update this question.

1. First, make sure your have installed “guest additions” (VirtualBox documentation describes how to do this). This may solve your problem. If not, go on.
2. To see what resolutions your screen is capable of, on your host machine go to “Preferences” and then “Screen Resolution”.
3. Create a snapshot of your virtual machine in case the below steps cause you problems. That way you can always revert back to a stable machine. (VirtualBox documentation describes how to do this)
4. In the terminal type:

sudo gedit /etc/X11/xorg.conf
(space after gedit and X11 must be capital X)

5. You now need to hunt through the text until you see the display resolutions listed. The ones you will be concerned about will be listed under bit depth 24 or bit depth 16 (as these depths are the ones that give you a large amount of colors.)
6. Next, either replace the existing resolution, or add another listed resolution in the exact same manner. Your resolution must be equal to or less than what the host machine is capable of (see step 2).
7. Restart the guest machine. Your resolution should be what you have specified or allow it to be changed.