How to upgrade or replace the RAM
*Although Apple's original specifications stated that these models shipped with PC100 RAM, Apple later noted that RAM must be "PC-133 compliant".
The 700MHz thru the second 1 GHz models use PC 133 sticks. The maximum RAM is 1 GB. The second two 1 GHz models and higher machines use PC 2700 memory sticks and have a maximum RAM of 2GB.
Lay a towel (to protect the screen) on your work area and place the unit face down with the bottom facing you.
The access panel is held in place by one Phillips screw. Unscrew it.
Unplug the machine after touching the metal housing to prevent ESD (electro static discharge)
There are two RAM slots. Release the RAM by pushing the white outer tabs. Then pull the RAM straight out.
Place new RAM in slots and press with both thumbs on each end till you feel them seat.
Replace the access panel. Turn it over and plug it in. Boot the machine up and click the Apple logo in the menu bar and then go to "about this Mac", to check to see that the RAM is being recognised properly.