RDP Login

When I open RDP to start a new session, the [User name] field has a
domain pre-pended to the user name, as in

"domain\user name"

That requires me to manually delete "domain\" as the correct login is
"user name" not "domain\user name". How can I cause the XP RDP client
NOT to pre-pend the domain to the user name?

Also, on some clients, logging into "domainname.com /console" works. In
others, it spits up with ["domain.com /console" is not a valid address.]
Why does one work and another one does not?