IDE drive jumper notesWhen connecting IDE drives, you must set the jumpers properly for the drives to work. IDE drives have Master and Slave settings, and you can only have 1 Master and 1 Slave on the same cable. Some drives (most notably Western Digital) also have a special Single drive setting for when a drive is the only drive on the cable.
Most drives have their jumper settings printed on the label, some have a manual that comes with the drive that shows the settings.
In general the jumpers are located in a small jumper block on the back of the drive betwen the power connector and the 40-pin IDE cable connector.
Here are links to the manufacturer's information on jumper settings: