i dont knwo how much it supprts, but there is a prog in the download section that fixes problems and helps support mroe then 512mb ram, im pretty sure there is, i was looking through the download section yesterday.
98 & me should be able to use over 512MB ram, most likely the limiter is your hardware. Your motherboard will have 2, 3 or 4 SDRAM slots, and each slot will be able to address a maximum of 128, 256, 512 or 1024 Megs, as it stands right now. That varies greatly between motherboards, but to answer your question, XP can address 4GB or RAM, if I remember reading that correctly.
EP, glad to see you come back and tidy up...did want to ask a one day favor, I want to enhance my resume , was hoping you could make me administrator for a day, if so, take me right off since I won't be here to do anything, and don't know the slightest about the board, but it would be nice putting "served administrator osnn", if can do, THANKS