VirtualBox cannot display full screen, screen resolution is not correct. 1) Windows The solution is "Devices > Install Guest Additions...", after that one more drive will be appeared in VM. Install VBoxWindowsAdditions, a screen resolution problem will disappear. Moreover, you can seamlessly move the mouse between ubuntu linux ( or whatever OS ) and windows 7 ( or whatever ) inside VM without pressing Host button ( Right Ctrl ). After that, you can change CD/DVD ROM, back to your CD/DVD drive in order to use CD/DVD ROM in VM. 2) Ubuntu Install Guest Additions 2.1) "Devices > Insert Guest Additions CD image..." 2.2) Install necessary packages $ sudo apt-get install make gcc linux-headers-$(uname -r) 2.3) $ sudo /media/cdrom/VBoxLinuxAdditions.run Change Screen Resolution VirtualBox : Virtual Screen > Resized to 1024x768