pls come inold sdrams use 128Mbits per chip technology which is expensive whereas the latest ones usually use 256Mbits tech which can significantly reduce the cost but cannot be fully recognized by old style of laptops. for example, the pc100 sdrams in the market are all assembled using 128Mbits chips and a 256MB one usually cost you around 150 dollars. for pc133 sdrams, both techiques may be used. that is the reason why the prices for pc133 vary that much. therefore, before you buy, you must get a clear idea what kind of chips the memory is using and whether it is compatible with your laptop. the best way is to bring your notebook to the store and test the rams there.