xp on multiple os networks

I HAVE SEVERAL XP, NT, 98,95 & ME RUNNING IN THE SAME ENVIROMENT BUT THERE IS ONE SINGLE XP USER WHO KEEPS ON CALLING ABOUT HIS WORKSTATION.

THE TROUBLE IS WHENEVER HE OPENS OFFICE DOCS IN TAKES SEVERAL MINUTES LIKE SAY 25/40 TO OPEN WHEN HE HAS HIS NETWORK CONNECTION OPEN. IF YOU DISCONNET IT THRO' TASKBAR SHORTCUT AND RE-OPEN THE DOC EVERY IS FINE. THE PERSON HAS NORTON ANTIVIRUS AND DIAL CONNECTION.

I HAVE CHANGED PCs RE-INSTALLED, FORMATTED, ETC NOTHING SEEMS TO CHANGE

PLEASE ADVICE.