Dell Dimension 9100 - Manual (Page 17)

12. 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.
13. Close the card retention door by snapping it into place to secure the card(s).
14. If you installed a card, connect any cables that should be attached to the card.
See the documentation for the card for information about the card cable connections.
15. If a card retention mechanism is present on your computer, reseat it in its tabs, and rotate it down until it snaps into place.
16. If a "piano" bracket (for full-length PCI-E cards) is present on your computer, rotate it down into place.
17. Replace the computer cover , reconnect the computer and devices to electrical outlets, and then turn them on.
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 port or device and then plug the cable into the computer.