This worked for me on my laptop:
1)
Open settings.xml:
C:\Program Files (x86)\Windower4\settings.xml
2)
Add a resolution that makes sense for your monitor between the 'profile' tags:
https://pasteboard.co/GTGeaFR.png
3)
Launch FFXiConfig:
C:\Program Files (x86)\Steam\SteamApps\common\FFXIPAL\SquareEnix\FINAL FANTASY XI\ToolsEU\FINAL FANTASY XI Config.exe
4)
Make the resolution in FFXiConfig match the one you entered into 'settings.xml'