Just been trying out virtual box on my iMac seeing as Parallels 6 won't work on Mountain Lion. Got everything installed no problems, Windows 7 up and running and guest additions installed. Only problem I have is that VB doesn't anywhere near fill my 21.5" iMac monitor. At best it's only filling half the screen, even on full screen mode it's no different. All that happens then is the screen is filled by empty border. Is there a way to get a full screen Windows 7 VM e.g. like Parallels or Virtual Box?