Sony VGN-CR490EBL - Manual (Page 121)

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Upgrading Your VAIO Computer
8 Slide the memory module into the memory module slot and push it in until it clicks into place.
!
Do not touch any other components on the motherboard.
If you use only one memory module, be sure to insert it to the upper slot.
Be sure to insert the connector edge of the memory module into the slot while aligning the notch on the module with the small projection in the open
slot.