Manually Setting Monitor Screen Resolution
Note: Be warned that serious damage can result from entering settings that your monitor does not support.
Step by Step Procedure
1. Goto the run command box, type: regedit, clk ok
2. Left clk/highlight the HKEY_LOCAL_MACHINE Folder
3. Clk the edit button then clk find.
4. Type: resolution, clk find next.
5. Right clk resolution, clk modify
6. Enter the proper resolution figure in the value
data box. IE: 800,600 Clk ok,close Reg Editor.

For informational purposes I had
one monitor whose display was narrow in width & looked
slightly taller than normal.
As it turned out the settings were something like 723x667.
Don't have a clue as to how it ended up with the odd settings,but
when I set them @ 800x600 everything was fine.