Hey
rolli59 gave good advise. I probably wouldn't go over the 2 GB total ram though. I don't think your current system really warrants it. You should maybe think about having a look on ebay for your parts to, you may save some money on the ram. It is older, so people may be looking to give some away for next to nothing.
note: my motherboard not recommend me to use PC-5300 mem. module because i'm running at 533 Mhz FSB processor....
what should i do? any recommendation?