I have a Dell Dimension 4500 computer that only has 128 mb of RAM installed and I wanted to upgrade it to at least 512. So, I went to the Kingston.com website and put in the computer info and it told me that I needed to purchase DDR PC2100 memory. I went to a local dealer and got the memory, and when I installed it, the computer worked fine for a minute and then it started freezing up. I went back and switched the memory around every way I could think of and finally, I just took the old memory out and kept the memory I had just purchased in. Nothing!!!! When I restarted the computer, the icons on the desktop wouldn't even come back up! Does anyone have any clues as to what I am doing wrong?????