HIDE WINDOW ERROR

WHEN WINDOWS IS STARTING THIS “HIDE WINDOW-ERROR” POPS UP AND EVERYTHING FREEZES FOR ABOUT 30 SECONDS THE ERROR IS “WINDOW NOT FOUND”
THE SAME THING HAPPENS WHEN YOU START INTERNET EXPLORER THE LOADING OF APPLETS IN IE SEEMS TO BE SLOW AND IE IS FROZEN FOR ABOUT 30 SECONDS.
500 MHZ PC RUNNING WINDOWS 2000