Merging and Creating Windows ISO’s

Hello, I was just wondering if anyone could show me how to merge multiple Windows ISO’s and make it into one big bootable ISO. I just got a free dreamspark account from school and downloaded multiple versions of Windows (Vista, 7, 8, 8.1). I have both x86 and x64 editions of each windows. I was wondering how I can merge all the ISO’s I downloaded and make it into a bootable ISO that allows me to choose which Windows I want to install. I plan to make a bootable USB drive out of this. Thanks.
Answer #1
Win 8.x � Win 7 � Vista – ‘Multi-OEM’ ISO Project:
http://forums.mydigitallife.info/threads/15733-Win-8-x-%95-Win-7-%95-Vista-Multi-OEM-ISO-Project