Ubuntu – Unable to run Windows 8 in full screen mode in VirtualBox on Ubuntu 12.10

Gues additions seem to been installed correctly.

Can you give your graphic card 32 Mb of memory. It's the only difference that I see with my setup that does work correctly in fullscreen or seamless.

How to check if video guest additions are installed

Looks like guest additions have not been correctly installed. Check that windows is using Virtualbox Graphics Adapter as it's display driver. If it isn't try to reinstall the guest additions and report back any problem that it displays.

You can check it using the Device Manager on windows. If you are using XP, you can reach it this way:

• To open Device Manager, click Start, and then click Control Panel. Click Performance and Maintenance, and then click System. On the Hardware tab, click Device Manager.

Other windows version have it placed in another places, but it's always there ;).

Virtualbox 3.2.12 has been out for a while, maybe that will fix your issue