VirtualBox Installation Host Screen Size problem

[bonnevie]

Hello,
I'm stuck with a screen problem in Virtualbox:  the bottom part of the setup instructions in Host is hidden and I can't move the panel around to unhide it. I should see buttons like  "Continue" or "Cancel". Because it's [below the screen], I can't move on. It looks like this:


 
(OVF file was removed before posting)


VB was downloaded from Light Software. My max screen resolution is 1366X768. Lowering screen rez is only giving me the same truncated VB image (with black margins) and I still can't move it around. I know these buttons are down there, so it's kind of frustrating!
I welcome any suggestion to get a full screen.