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Very usefully, I could find the trouble clearly with that manual.
Text excerpt from page 57 (click to view)
installing a Memory Module
6
Tighten the screw on the memory bay cover.
� Your notebook comes with a memory module installed in the memory slot. To upgrade
your memory, removal of these modules may be necessary before installing your upgrade memory module.
installing a Memory Module
1 2 3 Follow steps 1 to 4 of �Removing a Memory Module� on page 30 for removing the preinstalled memory. Remove the new memory module from its packaging. Install the memory module by sliding it into the memory module slot. Press the module into place until it clicks.