HP d325 ST Hardware Reference Manual page 56

Hard Drive Installation Guidelines
18 inches maximum total length, 80-conductor cable with maximum spacing
of 6 inches between Device 0 and Device 1.
80-Conductor Ultra ATA Cable
1 Device 0 (primary drive) connector
2 Device 1 (secondary drive) connector
3 System board connector
For optimal performance, connect hard drives to the primary controller. Connect
expansion devices, such as ATA optical drives, tape drives, and diskette drives,
to the secondary controller.
Install either a third-height or a half-height drive into a half-height bay.
Install guide screws to ensure that the drive lines up correctly in the drive cage.
HP has provided extra guide screws installed in the front of the computer chassis
behind the front bezel. Some options use M3 metric hardware. HP-supplied
metric screws are black. HP-supplied standard screws are silver.
If only one device is connected to a cable, that device must be attached to the end
(Device 0) connector.
If you have only one device, make sure to connect it to the Device 0 connector. If you
connect it to the Device 1 connector, the system will not recognize the device and
you may get a "no fixed disk found" error message.
B-2 Hardware Reference Guide