lasheenakillsnight - go to support.dell.com. Click on HOME support. Enter the service tag of your Dell computer. The service tag will be on the top or side of the case, usually on a black sticker. And it's also on the back of the computer on a white sticker. It's about 5 or 6 characters. Once you enter that you can view all aspects of your PC and somewhere you will see the specs and it will say exactly what kind of RAM you need. Not all RAM will downclock properly. It's best to try and have all memory the same speed if possible but many times it will still work if you mix different types.