Outlook Web Access

A computer won't let me access outlook web access from a user account. I can access it from a different one. It is the e-mail for a school the computer's owner works at. I've run avast, adaware, spybot, and windows registry repair pro but still have the problem. Do I need to reinstall the IE browser or run a system restore. Also I can't run windows update from this computer. It doesn't give me an error code it just won't let me do it. Do I need to reinstall the OS.