Dell OptiPlex GX520 - Manual (Page 79)

8. Attach the serial ATA connector removed in step 5 to the first hard drive.
9. Locate an unused serial ATA connector on the system board and attach a drive cable to this connector and to the second hard drive.
10. Replace the computer cover .
Drive-Panel Inserts
If you are installing a new floppy or CD/DVD drive instead of replacing a drive, remove the drive-panel inserts.
1. Follow the procedures in " Before You Begin ."
2. Remove the drive panel by sliding the drive release latch downward to open the panel. Then remove it from the hinges.
1 hard-drive cable
2 hard-drive cable on system board
3 power cable