i'm having a little problem with windows 2000

is not acting like how it used to act.......lately it has been freezing up.......so i went to the task manager and checked to see what was taking the greatest process and i notice that explorer.exe was taking 99 of the cpu process, and i tried to end the process so it would take all of the icon and bar from the desktop..........do anyone know what type of problem is my OS experiencing..............tanx for the help in advance.