7.Now connect the hard disk drive ribbon cable. As shown below, there is a tab on one side of the connector, just like the diskette drive connector. The hard disk drive socket at the front of the main system board also has a notch on one side.
hard disk drive connector
tab
hard disk drive socket
Align the connector with the socket so that the tab on the connector lines up with the notch in the socket. Make sure the holes in the connector fit over all of the pins in the socket and then push the connector onto the pins.
Caution
If you do not correctly align the holes with the pins in the socket, you could severely damage your computer when you push in the connector.