Sony PCG-XG28 Primary User Manual page 116

Follow steps 1 to 5 of "To install a memory module."
Touch a metal object (such as the connector panel on the back of your
computer) to discharge static electricity.
Remove the memory module.
Follow steps 8 and 9 of "To install a memory module."
Shut down your computer and disconnect all peripheral devices,
such as your printer.
Unplug the computer and remove the battery packs.
Wait until the computer cools down. Then unscrew the screw at the
bottom of your computer.