Dell Dimension E521 - Manual (Page 27)

When you install a drive, you connect a DC power cable and a data cable to the back of the drive.
Drive Interface Connectors
The drive cable connectors are keyed for correct insertion. Properly align the cable connector key on the cable and the drive before connecting.
Connecting and Disconnecting Drive Cables
When connecting and disconnecting a serial ATA data cable, disconnect the cable using the pull-tab.
Hard Drive
Check the documentation for the drive to verify that it is configured for your computer.
1 power cable 2 power input connector
1 interface cable 2 interface connector
CAUTION: Before you begin any of the procedures in this section, follow the safety instructions in the Product Information Guide.
CAUTION: To guard against electrical shock, always unplug your computer from the electrical outlet before removing the cover.
NOTICE: To avoid damage to the drive, do not set it on a hard surface. Instead, set the drive on a surface, such as a foam pad, that will sufficiently
cushion it.
NOTICE: If you are replacing a hard drive that contains data you want to keep, back up your files before you begin this procedure.
NOTICE: To prevent static damage to components inside your computer, discharge static electricity from your body before you touch any of your
computer's electronic components. You can do so by touching an unpainted metal surface on the computer chassis.