Over the past few days I have been trying to dualboot Windows 8 on my mid-2010 MacBookPro because I want to game out to some Skyrim and finish the storyline. Unfortunately, when I use the BootCamp Assistant I have no option to create a Windows 7 USB installer. On the second screen where you can download the Apple Windows drivers and perform the install, there should be a checkbox to create a Windows 7 USB install disk. The funny thing is, I could have sworn I had seen this option enabled before. Well on my MacBook this option was nowhere to be found.
I did some googling and I stumbled across this thread which outlines that the BootCamp Assistant does not have the current Mac in its “support Macs” plist file. By editing the Info.plist in the Package Contents of BootCamp Assistant.app and adding my MacBook into the file, I was able to create a Windows 8 install disk with the BootCamp Assistant.
If the thread mentioned earlier does not work, the information is in a more condensed version on the Apple Forums.