Good morning! Recently my iMac's HD stopped working. After unsucessfully trying to backup its files and formatting after already having opened the whole thing up, I decided to buy a new HD. I follow the instructions on this link. My iMac is also exactly the version shown, a 21.5" EMC 2389. Turns out the HD's thermal sensor cable connector doesn't fit the new one, also as reported, it has an extra tiny bit of plastic. I decided to leave it unplugged and assumed that's okay. Please correct me if I'm wrong. I read it should make the fan run at full speed, but I wouldn't mind if that happened as I live in a hot, hot place and experience overheating problems way too often. The problem is, when I screwed it all back together and turned it on, it once showed me the white screen with the folder and the question mark. I then went over to my other computer to prepare a bootable pen drive to install the OS and came back only to find it wouldn't turn on anymore. I can hear the fans (definitely not at full speed though) and a bit of the HD, but the screen is black and there's no chime. I opened it back up a bunch of times to check if I had properly connected all wires and think I did. There's only the sync cable, the LED cable (two black little ones) and the LCD data cable plus the LCD thermal sensor, right? I really don't know where I have gone wrong. Maybe it's relevant to say I also installed more RAM. Any input is appreciated. Thanks in advance!