Why won’t Outlook connect to Exchange server 2003?

I am new to Exchange Server 2003 and I have a friend with a network server that I don’t know how to re-establish a user to the network. I moved one of his non used computers to this station and now when I try to log in the user I get the error that the name can’t be verified because Outlook is not connected or online. This computer used to be online with a different user. Can anyone tell me the steps to check this? Thanks.