Hi, I am having issues installing Windows 8.1 on my iMac 2011 27". When I go on Boot Camp, there is no option to create a bootablee usb (I also have a Macbook Air). What are the options I have? I did look up to see that you could edit the Boot Camp plist and add some lines to it to enable this option, but I opened the plist and the code has changed for Yosemite. Will I have to burn Windows 8.1 onto a DVD?