Dell Dimension 2100 System Reference Manual page 62

c. If the module is difficult to remove, gently ease the module back
and forth to remove it from the connector.
4. To insert a module, press out the securing clip at each end of the
memory connector.
5. Align the notches on the bottom of the module with the crossbars in the
connector.
NOTICE: To avoid breaking the memory module, do not press near the
middle of the module.
6. Insert the module straight down into the connector, making sure that it
fits into the vertical guides at each end of the connector.
Press firmly on the ends of the module until it snaps into place.
If you insert the module correctly, the securing clips snap into the
cutouts at each end of the module.
NOTE: The system memory value reported by the operating system is 1 or 2 MB
less than the memory installed because that memory is reserved for video
functions.
Heat Sink
1 Heat sink and fan
assembly
2 Heat-sink securing
clip
3 Microprocessor
4 Microprocessor
socket
5 Heat-sink securing
tab