I have a late 2007 iMac with El Capitan installed. I am trying to install Windows 7 with a Windows 7 upgrade disc. My internal DVD drive broke, so I have an external drive that I am doing it with. I run through the bootcamp process, get to the rebooting step and the computer remains gray. I was using an old external DVD Drive so thinking it may be not functioning as expected I bought a new one (http://www.amazon.com/gp/product/B00ODDE33U?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00) thinking that was the issue. It turns out it was not. I tried rebooting hitting option and selecting the EFI Boot (the portable dvd drive) option and it hangs right where I click it. I tried other Windows discs (Windows 7, XP, 8) and have the same exact issue. Anyone ever encounter this?