Windows98 Auto Netowork Logon

To whom it may concern:
A user on our network has been having many problems logging on to the network. Actually her computer is doing it for her. She is never asked for a user name and password in the morning when she logs on to her computer, it just automatically logs on for her on to her network. After about 5 hours of work or so, she loses all of her network connectivity and she has to reboot her machine which it then logs on automatically again. Is there any way to get rid of thisauto logon? Is there some type of setting that logs her on automatically and then after so many hours of log time she gets logged off or something? I don’t know, PLEASE HELP!!!!!