Outlook can’t start

Our server was infected with the Nimda virus. After the techs worked on the virus and told us we could come back online, my outlook would no longer work. When I clicked on it, I got the message “Outlook can’t start”. I am also unable to set a default printer on both my NT 4.0 machine and my 2000 Pro. Our server in WINNT 4.0 and I have both nt and 2000 machines I use. My Explorer is also having some strange actions. It often freezes up and says there is an error and to restart. Any suggestions as to what has happened? HELP