I need to set up dual screen. I've tried countless of ways but failed. Right now, I have re-installed x server so everything is at it's default. How do I switch to dual monitor with one being portrait (and left of) the other, the main screen?
I would recommend using Nvidia-Xserver-settings for that if you have an Nvidia card (guess so from post title).
If you want to automate the process you can also consider using Disper it was my life saver for everyday use of dual monitors.