a desktop pc ram (memory) looks like this below: this is SD-RAM [img]http://www.technibble.com/articlecontent/types-of-ram/SD-RAM.gif[/img] this is DDR RAM [img]http://www.technibble.com/articlecontent/types-of-ram/DDR-RAM.gif[/img] this is RAMBUS ram [img]http://www.technibble.com/articlecontent/types-of-ram/RD-RAM.gif[/img] visually, you can easily identify what type of RAM your motherboard can support thru the notches (the slot or space you can find along the gold plated part). each one of them have different clockrate. commonly, if you don't have the manual of your motherboard its hard to identify if what ram your motherboard supports tha ram that came along when you bought your PC hav stickers on them and you can find there is indicated the clockrate like for example PC133 which has a clock rate of 1330Mhz. others have PC400 and so on.... if this helps, a thank you is appreciated...