Dell XPS 730 H2C (Late 2008) - Manual (Page 20)

8. Connect the power cable to the hard drive.
9. Connect the hard drive data cable to the hard drive.
Dell XPS 730:
Dell XPS 730X:
1 hard drive 2 hard drive bay
CAUTION: Ensure that all connectors are properly cabled and firmly seated.
1 power cable 2 data cable