I installed Xubuntu onto my HP 2133 Notebook, installed all the updates and everything was working fine. I wanted to use an external monitor to extend the desktop between my laptop and monitor. The monitor displays a picture fine, it mirrors what is on the laptop but I can't change any settings for the monitor, such as the resolution. In display settings no other monitor is displayed, it just shows the 'default' monitor which is the laptop and I can only change the resolution of that.
I've looked at several answers to this kind of problem but the answers are just about setting up multiple monitors when the computer detects the external one, but my problem is that my laptop won't even show settings for the external monitor, like it's not there.