Ways to help me computer run faster?

I have an old computer with 2.4 ghtz processor, with 2 1gb sticks of ram running at 133 speed. Also I have a radeon x1500 agp Video card. I am using Windows Xp service pack 2 operating system. I was wondering if there was any ways that I could clean my computer out and make it run at optimal speeds because I have been having some freezes and hiccups in my games. I am looking for both general things and also some specific things that could help certain pieces of hardware run better and faster. Thank you for your time, and your answers.