There are a load of superfluous services that XP starts up by default. One of the worst is the automatic system restore service.
By following the some of steps detailed in this excellent website..
blackviper.com
I greatly reduced random disc access and speeded up windows XT.
NB: If you want to "tweak" XP, make sure you know what you're doing.
Of course, you could always install a proper operating system........