I have windows 10 installed on a UEFI system. I'm looking to install Windows 7 Pro 64 bit to have the option when I boot between Windows 7 and Windows 10. The problem I think is that it's a UEFI system. I've tried going into the BIOS and putting in into legacy support mode. I've got a USB with Win 7 on it, and a partition (on the hard drive windows 10 is installed onto) created for the install. When I boot into Win 7 setup it gets as far as selecting the drive to install to, but it won't let me install onto the set aside partition. It says "windows 7 cannot be installed the selected disk is of the GPT partition style". I tried googling the problem, but I honestly have no idea what I'm doing, and don't understand the possible solutions. Does anyone know how to help me? And if you do, can you put it in such a way that an idiot like me can understand?. Thanks.