Hi, I have an HP xt948 with a ASUS P4B-LA (Amazon) motherboard. I only have 256MB of 133MHz SDRAM, I'm a little too rough on my computer for that amount of memory and it's causing me problems. Money is a little tight right now so I'm trying to scavenge parts from some old computers that are sitting around. I found 3 sticks of Apacer 128MB 100MHz in 1 case and 2 sticks of Liberty 512MB 133MHz DDR400 PC3200 in another. In an ideal world I'd like to take out my 256 and put in the 2 512's. But I get the impression the DDRs aren't compatible. Is that true? If it is, would it make sense to switch out the 256 for the 3 128's (to keep the speed the same). Or since they're slower (100 vs 133) would the speed loss counteract any benefit of an extra 128MB? Any advice would be much appreciated.