Well, I don't know that particular model, but here are Dell's instructions:

http://support.dell.com/support/edoc...ce.htm#1154906

They suggest that you take out your existing drive and put it in the bottom slot, then put the new drive into the top slot.

CONNECT THE END CABLE CONNECTOR TO THE FIRST (bottom) drive and the middle connector to the second drive (the new one that is now in the upper slot)

Dell are using "cable select" (CS) so make sure that your HDD jumpers are set to "CS"

Then you should be good to go.

From what you are saying, you either misread the manual, or there is an error in it?