How to focus a computer screen

I have just changed my computer screen to a bigger screen. The problem is that the screen is out of focus with weird shadows next to the words. The screen is an odd size so my operating system is having trouble with the resolution, I think this is why I am having trouble with the focus.
The forums on the internet all say to either buy a newer more expensive monitor or open it up with a screwdriver and fiddle with various internal things like, vacuum tubes and knobs.
The screen itself has a focus setting under it's general settings. So I am hoping to not have to open up the screen or buy a new one. The screen is very difficult to read things off of, it is OK for movies but I want to be able do more with my computer than watch movies.

it's not uncommon to have "ghosting" problems like you describe when using an analog connection to a monitor that does not support the resolution you are sending it.

Does your monitor have an "auto" button/command? I'm not sure if that's what you mean by "focus" under the settings. When you push it, you'll see the monitor to try to crispen up.

Try switching to a lower resolution. For example, I've never seen, even oddly shaped monitors, that couldn't render fine at 800x600.

I assume you have an LCD or LED flat panel display, not an older CRT type.

Best results are when the resolution setting in your computer match the native resolution
of the display. You should have that information (native resolution) if you bought it new.
Or look up the information using the model no. at the manufacturer's website.

If you can't match the computer resolution to the display, look for a clock adjustment in
the display settings and try adjusting that.

In a CRT monitor, shadows are not focus problems. Those are usually either frequency response
problems (like ringing on the fast signal edges) or a convergence problem where one of the three
colors is displaced from the main image.

My monitor does have an auto configure but it does not affect the focus.
Changing the resolution eventually did it but 800 x 600 is way too small, it made the icons too big and most of the programs either extended off screen or covered everything else up.
Eventually I found a resolution my OS liked that looked OK with little or no shadow, reasonably sized icons and program windows.

The problem was that the OS's resolution options did not extend high enough, eventually I just did trial and error till I got one I liked.

how old is the computer you're connecting it to? anything made in the last 5 years should be able to drive a 720p or 1080p-sized monitor.