Upgrade boot camp assistant?

Hi!

I have a retina macbook pro with boot camp assistant version 5.0.3. No problems installing windows on my comupter. However, when I want to help my friend install it on his macbook pro (maybe 3 years old), with boot camp assistant version 3.xxx and it does not compute how I want it to. It does not give me an option to select my Windows 7 ISO file, and the installation-process is not the same as the one on my macbook retina. My question now is how do I update my boot camp assistant to version 5.0.3? I have downloaded the 5.0.3 Zip from Apple but do I really need to drag it all over to a USB and do all that? Is there not any easy way to just simply upgrade Boot Camp assistant?