i had another topic on here, but recently ive talked to more and more ppl that have had this problem. is it possible that xp or my mobo doesn't accept two different brand of 512mb ddr chips. i have elixir and infineon. should i just sell the infineon and buy another elixir. that way i have two matched 512mb elixirs. would that basically solve everything?

I'm using 2 infineon and 2 samsung and i never had this type of problems. I don't think the brand of the memory is your problem here, may be your problem is a bad slot.

each one works individually by itself while clocked at 266mhz frequency. when i have them both it they dont work unless i lower the frequency to 200mhz. (which is slowing down my cpu by the way right??). i guess at this point i can either run 1 512mb 266mhz or 1gb (2x512mb) at 200mhz. which would u do? maybe i can go with a different OS like 2k or even 98. what really bothers me is that when i originally built this computer, the two ram chips and system was working fine. just one day xp decides there incompatible and wont even let me boot into the OS, even after formatting numerous times, is what confused the hell out of me.

Some motherboards may have a problem with different brands of memory. Mine specifically lists some brands that are "not supported." If each stick works on its own, then return it for the same brand as your original. If the new one does not work on its own, it might just be a bad stick.

aaron, I believe that you have two different speeds of ddr ram. One speed,pc1600 and another one running at pc2100. Have you looked up the numbers for the ddr? On the chip there is printed number on the ddr do a search and see what number corresponds to that stick. Majority of motherboard manufactures do not recommend using two different speeds of ddr in the boards. So you really should check the motherboard manual and see if its ok.