Do you know who manufactured the GPU?
In any case, right click an empty area of the desktop.
A small menu should appear with "Show more options" at the bottom. Left click that choice.
Another small menu should appear that includes the manufacturer's name followed by the words "Control Panel.
For example on my computer the menu item is listed as "NVIDIA Control Panel".
Left click that choice and the applicable Control Panel should open.
There will be more options and on my system under "Display" I can select 1920 x 1080 via a resolution menu. Or select other supported resolutions if and as required.
However, if your systems does not support 1920 x 1080 then that resolution should not appear as an option. Or be greyed out accordingly if it does.
Hopefully your Control Panel will list 1680 x 1050 as a selectable resolution.
If the Control Panel is not clear then take some screenshots and post the screenshots here via imgur (
www.imgur.com).