you should look on it really close use a magnifier if you have to and see if it says: "sdram" or "ddr ram" since certain computers take either or since i doubt its ddr 2 at that speed.. also look for a band name like kingston, mt, micron etc. some "cheaper brand" ram sticks dont have any writing on them too i hate that! >.<
also there should read "pcxxxx" where the x's would be numbers like pc2100 just an idea that always helps :)