Hi. I have just replaced the HDD on a 2007 iMac with a Kingston 240GB SSD. I followed the iFixit guide and everything appeared to go smoothly. However when I try to boot the Mac into start-up mode (holding down the Option key) it get's stuck on a white screen with a movable cursor. All other boot modes (normal, Cmd+R, C, D etc) result in the folder with the flashing question mark. I've got an El Capitan USB install disk prepared and connected but I cannot get to the start-up stage. I have tried using this install disk on another Mac and booting with the Option key held down worked fine. Stuff I've tried: SMC reset NVRAM reset Booting with nothing attached Booting with wireless keyboard and trackpad Booting with wired keyboard and mouse Unplugging power cable and leaving a while The Mac once displayed an image of an HDD with a globe sitting on top of it, which I can weirdly find no mention of on the internet! All other attempts have resulted in a white screen with a movable cursor (or the folder with question mark). So, does anyone have any ideas? Could something that happened when I had the Mac open result in this type of behaviour? The SSD I installed was not formatted but as I understand it that should not be a problem. Thanks in advance.