cant install new 1333 2gb pc3 -10600 cl9 240-pin dimm on my ax5810

ram slots are very specific. They normally only take 1 kind of ram. If you have 2 sticks of differing sizes, one is wrong. Look on the side of the stick that works. There should be a paper tag on it with the type of ram, the timings and voltage. look at the slot in the ram and the corresponding notch in the dimm slot. When they are matched up, do the edges fit into the slots all the way to the end of the dimm slot? It should fit exactly.