Exchange connectivity

Hello
ok I have a workstation windows 2000 with office 2003 business edition now i can connect to the mail server with pop3 access but not with exchange.
I can ping the server by name and ip, so dns is resolving.
I have added the ip and name with reverse (name then ip) into the lmhost file just for incase.
The unit did have office xp on it but I removed it and installed 2003 to try and get the communication going again but to no ends.
The user if I log her on a nother system has got no problem connecting the mail server so definatly a isolated problem.
every time I try to connect using exchange the message tells me cant connect to the exchange server and that outlook has to be online to do so.
What can I look at next

Kind regards