The IDE bus is used by the bus that the hard drive and other peripherals to connect to the motherboard. The cable that connects the motherboard to the hard drive is usually a flat gray ribbon type cable with one red colored wire. The cable must have the red wire on the LEFT side of the plug-in when inserting it into the mother board.  The red wire must be on the RIGHT side when connecting to the hard-drive and CD-ROM. Ideally each peripheral has its own cable to operate on.