If you choose that option instead of Try an Unlisted ISO, Yumi will install the Windows Vista/7/8 file to the root of the flash drive, and you DO NOT want that. It will work just fine if you install it as an unlisted ISO. So select Try an Unlisted ISO and then browse to your Windows ISO, then proceed with installation and you should see something similar to the image on the left. As you can see Yum is installing Windows 7 to D:\multiboot\ISOS\WIN7_MSDN.iso, which is what we want instead of having Yumi install it to the root of the flash drive. Continue to repeat this process for all the ISO files you want to install such as Windows and any other ISOs that are NOT listed in the Yumi list (Windows EXCLUDED). ALWAYS INSTALL WINDOWS ISO BY SELECTING TRY AN UNLISTED ISO.