If the display isn't going full screen, on that 15.4 inch TFT LCD screen, the problem is the screen Inverter, or LCD screen itself.
90 PERCENT OF THE TIME the fault is the screen Inverter.
It isn't a simple screen resolution setting that needs to be changed.http://www.laptoppowerjacks.co.uk/advent-inverter/advent-7111-7107-8315-lcd-screen-inverter-as023217127-iv09140t-lf.html
An LCD screen does not produce light by itself,http://solutions.3m.com/wps/portal/3M/en_US/Vikuiti1/BrandProducts/secondary/optics101/
It needs an additional light source.
The additional light source is a Backlight.
A Backlight can be a CCFL, or a series of LED's.
The Advent 7111 Notebook PC uses One CCFL,http://www.screencountry.com/index.php?section=products&model=7111&brand=Advent&size=
A CCFL is a Cold Cathode Fluorescent Lamp.
Similar to Fluorescent lighting used in homes, and businesses, but on a MUCH smaller scale.
(Average size is 2mm Thick. Length is almost as long, as the LCD screen is in height. 2mm is close to 1/16th of an Inch )
A screen Inverter is used to convert the power from the laptop, for the Backlight, and LCD screen.
I don't have access to a Service Manual, for the Advent 7111 Notebook PC. I haven't had one come to my shop for repair.
I DO have years of experience at repairing laptops, and I see the Advent 7111 is just a basic laptop, as I HAVE repaired over the years.
If you wish, I can guide you step by step, in replacing the screen Inverter.
(MANY people go out, and buy an LCD screen, when the problem is a much less expensive screen Inverter. Afterwards they buy the screen Inverter. Too bad they didn't come here first)
Post back in a Comment.
[ The Advent 7111 Notebook PC is just a re-badged Quanta TW3M.
According to the source, you should see TW3M on the bottom of the laptop.http://www.uktsupport.co.uk/advent/laptop/7111.htm