HP Compaq Presario,Presario 4400 Hardware Reference Manual page 39

Computer Upgrades
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3–22
2. The memory module can be installed in only one way. Match the
notch on the module 1 with the tab on the memory socket. Push
the module carefully and firmly into the slot ensuring that the
latches on both ends snap into place.
Installing a Memory Module
3. Complete the procedure described in "Reassembling the
Computer" section of this chapter.
If a blank screen is displayed after replacing or adding a memory
module, the memory is installed incorrectly or it is the wrong type of
memory. Remove and reinstall the memory modeuls as previously
described in the "Replacing or Adding a Memory Module" section of
this chapter.
Hardware Reference Guide