I have a old Dell Inspiron 1300, has a stick of 256mb samsung ddr2-4200. On this sticker it says 1Rx16, I see this on all ram Ive searched and to what i know its a density indicator. My laptop can upgrade to 2gigs but im not sure whats compatible. I see ram say 1Rx8 1Rx16 2Rx8 2Rx16, how do i know what my laptop takes as for as this Rx reference?