Dell Dimension 8400 - Manual (Page 17)

8. If you replaced a card that was already installed in the computer and you removed the top of the retention mechanism, you may reinstall the top.
9. Before you lower the retention arm, ensure that:
l The tops of all cards and filler brackets are flush with the alignment bar.
l The notch in the top of the card or filler bracket fits around the alignment guide.
10. Press the retention arm into place, securing the card(s) in the computer.
If a card fan is not present in your computer and you are installing a graphics card that runs higher than 75 W, contact Dell to find out how to purchase a card
fan.
11. If you installed a PCI Express graphics card that runs at 75 W or higher, install the card fan. Contact Dell to find out how to purchase a card fan.
12. Connect any cables that should be attached to the card.
See the documentation that came with the card for information about the card's cable connections.
13. Close the computer cover , reconnect the computer and devices to electrical outlets, and then turn them on.
14. If you installed a sound card:
a. Enter system setup , select Audio Controller, and then change the setting to Off.
b. Connect external audio devices to the sound card's connectors. Do not connect external audio devices to the microphone, speaker/headphone,
or line-in connectors on the back panel.
15. If you installed an add-in network adapter and want to disable the integrated network adapter:
a. Enter system setup , select Network Controller, and then change the setting to Off.
NOTICE: Do not route card cables over or behind the cards. Cables routed over the cards can prevent the computer cover from closing properly or
cause damage to the equipment.
NOTICE: To connect a network cable, first plug the cable into the network device and then plug it into the computer.