Photoshop Elements problem

When i try to install Elements on my iMac Intel core2duo, the installer stops saying a file is missing.

I am installing from a dmg file which installed perfectly on my Macbook pro.

Any ideas what is happening?

I only use it for cutting out images as it allows me to follow the actual line of the image rather than the crop options found in other programs.

Is there a another program that will allow me the same sort of control.