As Kimber notes, you will do well to research your system's requirements and capabilities. If you don't have the docs that came with the PC, research your mobo/chipset on the internet. Among other considerations, be sure to determine the TAG RAM specs for your motherboard. This is the amount of RAM that the chipset can cache. Adding more RAM than this value may actually slow things down, not the effect you're hoping for. You'll also need to determine the type and speed of RAM your system supports, then check to see what's currently installed. You can then decide whether to add more RAM via an open slot or whether you need to buy new RAM. If you replace your memory, check to see if your system board will support faster RAM than currently installed (PC133 instead of PC100, for example). Keep in mind that taking advantage of faster RAM may require a change in jumpers or BIOS settings. Hope this is helpful.