Outlook 2010 on Windows XP - can't resolve name of server.

In my organization, I have two Windows XP computers with Outlook 2010 that will only use RPC over HTTP.  If I turn it off, it comes right back.   I keep getting a username/password prompt whenever I open Outlook, but the password is always rejected.  I'm using the same settings as on other computers, but this one just refuses to take them.  It says that it can't resolve the name - name of the server I'm assuming.  I am using Exchange 2013 in a domain environment.  Why won't this one computer take the typical settings?  Is there any way to reset this behavior?  Thanks!