If your drives are jumpered as master (and slave if applicable) and not cable select, then it doesn't matter which end the hard drives are connected to as long as the blue end is attached to the motherboard. If you're using cable select for one or more drives, here's what you need to do (information ripped straight from IBM's website):
- Systems that use Cable Select have a unique ATA/IDE cable. The jumper on the drive must be set to the Cable Select position. The position on the cable where the drive is connected determines whether the drive is the master drive or the slave drive.
- To determine if the system uses Cable Select, refer to your system documentation. You may also be able to tell if Cable Select is used by checking the existing drive jumper settings.
- Installing or replacing a drive in a SINGLE drive system: The jumper should be set to Cable Select and the drive should be attached to the end of the cable for systems using the newer style cables, or to the middle of the cable for systems using the older style cables. Older style cables have wires that are cut between the second and third connectors.
- Installing or replacing a SECOND drive in the system: The jumper should be set to Cable Select and the drive should be attached to the remaining connector on the cable.
SUMMARY: Positioning only matters when you use cable select, and the VAST majority of people do not use cable select mainly because there's no good reason to do so.