Monitor Question

I just bought a Dell XPS 410 computer with a 20" 2007 WFPWide Aspect Digital flat Panel display Monitor.

The image it produces, especially photos, appear wider than they should be.

I contacted the Dell salesperson about exchanging the WFP Wide monitor for a regular size and she  told me that I didn't need to exchange Monitors just to go to settings>display resolution to adjust the screen.

 

Please tell me in simple terms how to accomplish this. I do a lot of Digital Photography and the pictures are not proportioned correctly. Thanks, frankm