Had to switch from a widescreen display to standard display. How to narrow the display?

SOURCE: acer 19167W flat screen

Depending on the application you are viewing the picture in you can shrink the application window. You could reduce the size of the viewable area but that defeats the purpose of the wide screen which is to provide a better viewing experience (to quote the marketing types). It sounds like....since the wider screen really has nothing to do with your picture size....you might want to adjust your picture size independent of screens and applications. There are a variety of free products out there that can do this...and some are really nifty...perhaps better than the software you might now be using.

SOURCE: How do I adjust the image width on this wide

This is one of the problems with the wide aspect screen. Most images seem to fit best on the older monitors.
You can go into the video properties and choose one the the display types that best display your image. Unfortunately, by taking a normal (to us) image that looked just fine on an older monitor and displaying it on a newer, wide-aspect monitor, you're gonna distort the image or crop it in a way you didn't expect.
My advice is to experiment with the display until you find something you can live with.