the main thing that most people do is have too many programs installed, you also always need to clear the temporary files by using 'disk cleanup' this should make a big difference in the speed. You should really go through all your programs and get rid of almost all of them apart from the ones you really need, games are a real pain for slowing systems down especially when you have 10 games that are all large in size. The more RAM and higher clock speed the better too but only when the OS supports the extra power or it's useless.
