There seems to be a missing step here. All the while one is removing the cables from their sockets it is supposed that the screen which is quite heavy is suspended in mid air… no, you are holding it up with one hand while doing everything single handed while in all honesty it would be nice to have both hands if for nothing else to steady your movements. So. Lets add a step. Lets figure out a solution and use some kind of prop until the screen is removable.
This procedure can be VERY dangerous. Why? Because there is the possibility of a gravity disaster if you lose control of the screen and it falls before you disconnect the interface cables. I know. It happened to me. After studying the Apple directions I came to the conclusion that I would need both hands on releasing a couple go the cables and decided to tape off the screen in the open position - which I did very carefully and securely. What I did not account for was the tape not adhering. Needless to say when it came loose the screen fell and ruined the connector sockets (and my computer). This could also happen just trying to hold the screen with one hand while spudging the connectors apart with the other as well. SO. LAY THE iMAC DOWN! DO **N O T** GIVE GRAVITY THE CHANCE TO RUIN YOUR DAY like it did mine!
The connection of this cable is moot (and to the main drive too) if you purchase HDD Fan Control Monitor software that uses the SMART tech inside the drives to set the fan speeds. It was rather expensive but worth the $35