Dell 400 Owner's Manual page 87

Removing a PCI Express Card
1 Follow the procedures in "Before You Begin" on page 63.
2 Remove the computer cover (see page 68).
release tabs (2)
card retention
door
alignment bar
3 If present on your computer, rotate the lever on the chassis wall upward.
alignment guide
filler bracket
*may not be present on all computers
*lever on chassis wall
Removing and Installing Parts
87