XP Pro login problem

[Rodney]

We have a W2K AD setup here, but have some XP Pro clients
we are rolling out. With the W2K Pro clients, we are able
to login to other domains using accounts set up on those
domains by simply mapping the drives and selecting the
Connect using different user name option. When those W2K
client machines login to our domain in the morning, they
are prompted for their passwords to re-connect to those
other domain shares because they don't match the
id's/pwd's for our domain.

Apparently XP Pro won't allow for that same type of
interaction. It won't allow the user (or admin) to
manually enter any other domain name. It automatically
inserts our domain name into the user name log on
credentials.

Is there some way around this? We are having a problem
with a particular application which will not open until we
download and install and update. Unfortunately this
download site requires a login name and password, but XP
is sending our domain name\user name as part of the log on
credential, which is rejected by the server on the other
end.

Thanks in advance for any insight!