I have a Dell GX520 optiplex model (mini tower), and I want to upgrade its RAM. I currently have 1GB RAM and I want to upgrade to 2GB. All I know about RAM is its capacity, and I've heard about speeds lately like 400mhz, 533mhz, 800mhz, 1333mhz. I want to know what are the differences among them and can my PC support all those types of speeds or…