How do you fix your computer screen when you only see the right half of the desk

Picture please?

I am guessing this is an LCD screen and it is going out, if I understand you correct that you can barely see stuff there still.

How does it look when first booting and it shows the BIOS screen?

If this is a laptop then hook it up to an external monitor and see how it is. If it is a desktop then try hooking up another screen to it.

Sounds simple but could it not just be that the screen just needs to be recalibrated? Is there a button on your monitor saying auto. Or otherwise go into your monitor settings menu, and try changing the x and y of where you screen starts? But yeh A screenshot would help