Billye: A couple of months ago I was going to upgrade my 2 year old 350MHzpII. Instead I ended up building a complete new system. In reference to your question, the P3V4X will support up to 1G+ according to the ASUS Techs. Use the latest BIOS and drivers. Realize also that the board supports UltraDMA/66/UltraDMA/33--- not UltraDMA100. I am waiting(anxiously) today for UPS to deliver my new IBM 46G.7200rpm ATA/100 harddrive and the ATA/100 adapter card so I can run the faster HDD. Info on my system: 850pIII/100MHz, ASUS P3V4X/Apollo Pro133 Chipset/AGP/4X mobo,40G. Maxtor/7200/66 HDD,8.5 Maxtor/5400/66 HDD,256(PC-133)Micron RAM(cas2),Leadtek/WinFast/GeForce/256/32MB videocard,MAXI SOUND MUSE soundcard,Mitsumi Floppy, Acer/50x CD-ROM, Acer/10x4x32 CDRW, Antec/300w./Powersupply and new ATX case, larger heatsink with fans on CPU,Twin/Turbo slot fans on HDD,rear backslot fans(mounted next to videocard), Diamond/SupraExpress/ext.modem. PC WorldBench 2000 performance score-- 179. 3dMark2000 performance score-- 5913(first time). When the new HDD gets here, I will make it the master, remove the 8.5G and switch the 40g. to slave. Total cost including new IBM HDD and adapter card---$1459.00. By the way, the techs at ASUS and Leadtek were very helpful! Good Luck!!