Evo,
There are two versions of the i845 Chipset. One used PC-133 SDRAM (SDR) and the other Used PC-2100 SDRAM (DDR). Which on does he have, SDR or DDR?
If it is the SDR then it is not worth upgrading since that Chipset was such a poor performer. (The PIV needs a huge memory bandwidth in order to operate at its full potential, pairing it with SDR cripples the memory bandwidth for the PIV and chokes it.)
Take Care,
Richard