Every time I start the game it's resolution is 1024 x 768

[Badanti]

Every time I start the game it's resolution is 1024 x 768. I have changed it a hundred times to 1980 x 1200 but it won't keep the setting. I have tried changing the setting in NewProfile3.xml under ...\my games\Age of Empires 3\Users3 but it will not keep the setting. I have updated my graphics driver and have all the latest important windows updates.This is Windows 10 on an Alienware 15 laptop connected to an external monitor.

Any ideas?

[Eaglemut]

1980 x 1200? According to wiki, such resolution doesn't even exist. I guess you rather have 1920x1020.
Anyway, you can try toggling the "Disable display scaling on high DPI settings" option in the properties of your age3y executable file. If that doesn't work, toggle windowed mode in the game settings.

[Speedbump]

This might sound obvious but your monitor supports that resolution right?

[Badanti]

Yes LOL. I manually change it every time I start the game.

[Speedbump]

Right, I don't mean can you set it to that option though. If you have a monitor with a 768p screen, you won't be able to see 1200 pixels on it. Usually people I see with this problem don't realise their monitor isn't able to show that many pixels. And games usually default the resolution to the native resolution of the monitor.

If your external monitor does support that resolution, maybe it's defaulting to the resolution of your laptop screen? Whatever the issue is, it can be fixed by changing the settings in the settings file like you tried, right clicking the file, properties, read only, apply. Doing this however means you won't be able to save the settings after this until you uncheck read only.

[Penfookio]

Im having the same issue. It is not a monitor issue, its a software issue somewhere. Ive run this game in multipul resolutions mostly 1080. But now you try changing the resolution to anything but default it crashes and give a message of a fatel error occured and thats it.

[Penfookio]

Another thing is vailidating the files comes up with "1 file fail to validate and will be reacuired" message. This is even after a full uninstall + deleting of all user files. The crashes continue, But my wife computer does not have this issue. Both systems are running same windows 10 build. My guess is there is a setting turned on or turned off similar to the Legacy options that if turned off prevents this game from launching at all.

[Penfookio]

Weirdest work around but fixes the issue. launch the game, Then use Alt+Enter to go to windowed mode, Then change your resolution , Then take it out of windowed mode. JOYS of playing an old game on a new system lol best of luck