It doesn't get much simpler than this:

This is for the free program Irfanview 4 http://www.irfanview.com/

During Install - Remember to Untick also 'include Chrome web browser'

Edit | create custom crop selection | (Actual ratio from image) click on 'Save and apply to image' | use mouse cursor to drag the selection border lines (double headed arrow on lines) up or down, and left or right to cover the area you want to keep inside your 'box' | Edit menu, 'Crop Selection' (or hold down Crtl and press Y)

now go to: File | Save As, and Save the result as (name of file here)cropped.jpg ((or whatever file name you want).jpg - or whatever file extension you want). You can now close your original picture.

Now you can open your newly saved cropped picture in whatever program you want and do whatever you want with it :)