Where can I buy a digital version of Windows 7 for Boot Camp? I'm going to attempt to install Windows 7 via Bootcamp on my new Retina Macbook Pro.  Since it's lacking an optical drive, every tutorial / walkthrough that I find says I need an ISO version of Windows.  I can't seem to find any sort of direct download links / stores that don't seem shady though?  Where can I get a legit copy of windows in ISO format?
You can download it from here : http://www.mydigitallife.info/official-windows-7-sp1-iso-from-digital-river/

You will need to have the product key to install it. If you don't have one you can buy it from Microsoft store.