When we use Window XP lots of Page File created. These Page files work as a virtual memory. They are also cause of slow speed of RAM. You need to clean these files. You can do these automatically when you shut down PC.
From Start go to Control Panel. Go to Administrative Tools/ Local Security Policy/ Security Settings/ Local Policies/ Security Options.
In the right side click twice Shutdown: Clear Virtual Memory Page File. Enable it & select OK.
Now from next time when you shut down PC it will automatically delete Virtual Memory Page File.
There is another option to increase Ram speed. From Start go to run. Write "Tree". Click Enter. If you do this regularly you will get smooth speed of your PC.