You should have 1 GB memory installed, you need 1 Gb or more DDR PC3200 400MHz (Non ECC) memory module and install it on the mainboard near the default one. You should open the case (unplug the PC before doing it ) and search for the memory modules, ther should be some sockets free, here is where you have to add the new module. If you search on google for "VGC-RA830G ddr" you can find what you need, I found 1 gb module for 79 $
I've 2 DDR 400 modules here for free but I can't just pass them through the monitor