non stop running of explorer

While tring to run defrag, and scan disk they starte over before finishing. I know for a fact explorer is running in the background and writting to the hard disk causeing defrag and scan disk to start over. The problem is I can’t get it to stop running. I use a dial up for connection to the internet. I used ctrl+alt+delete to try
to shut down explorer but it just starts again. I have a fire wall and have give Iexplorer and MsnExplorer access to the net as well as outlook express. But explorer runs in the background even when I dont have the browser open.I am running windows 98 and office pro 2000.
Can someone give me info on how to stop explorer from running even when its not open? Than You.