Grab yourself a copy of
Irfanview and the plugins, the greatest free multimedia program out ever. IT does most of the thing the average person needs to and more.
To cut part of a photo out simply click in the left corner of the part you want to keep and drag to the right bottom corner - this highlights the area that is to be left and you can do various editing option tasks incuding Edit/Crop Selection which will get rid of the unwanted bits around the selected part.