Inspiron 5348 (all-in-one) display truncation

Hi, the unit "works" fine but yesterday at some point the display began truncating the information. The truncation begins with power-on. (you can tell by the dell-logo and all you can see at the bottom is the option for F12 -- boot etc. (shouldn't there be an F2 listed also?  Part of the screen (about 25-33%) is a lighter shade of purple (vs. the dell logo screens charcoal).  Not sure if a user was messing with _something_. 

It strikes me as an aspect ratio change or a an outright defect.  Ran the diagnostics under F12 and nothing turned up.  The 5348 has no buttons on the unit allowing access to on-screen monitor settings (eg aspect ratio)

Anyone ever encounter this? Anybody know how to get at the display settings for the machine?  thanks, B