Dell Precision T5400 (Late 2007) - Manual (Page 223)

Adding and Replacing Parts 223
10 Connect a power cable to the back of the hard drive.
11 Connect a data cable to the back of the hard drive and, if it is a SATA
drive, connect the other end to the SATA_2 connector on the system
board.
1 sliding-plate lever 2 optional third hard drive in FlexBay
1
2