I currently have 256mb of SDRAM PC133 on my machine. I was wondering if I am able to put in a stick of 256mb DDRRAM as well or are the two different kinds of ram incompatible? If so can I replace the SDRAM with two sticks of DDRRAM instead? I am not sure what motherboards support DDRRAM and if I can use it on my computer or not. Is there a good website that explains all of this? Thanks.