I bought two copies of Microsoft Office 2013 Home and Business. I have installed one on my desktop and one on my laptop. I thought that rather than download again if I had to reinstall I would download the offline version and burn to a DVD. I have duly done this twice and ended up with 'HomeBusinessRetail.img' (2.04GB) on the DVD and am unable to do anything with that file, if I double click it tries to burn it again. What am I missing?

Thank you in expectation.

Windows 8.1, 8GB RAM