Not a Domain User yet can access domain?

I installed Vista Enterprise. I set myself up as a member of the Domain as I
always have under XP. It joined fine. However the login name remained as
LOCALMACHINENAME\USERNAME not DOMAIN\USERNAME. I figured this was a
characteristic of Vista. I used the machine with no problems for two weeks.
One day when I booted my machine, the profile had changed to DOMAIN\USERNAME
and everything that had been setup in the profile, naturally, was gone.

I reinstalled. Went through the same procedure of joining the domain. It
still shows LOCALMACHINENAME\USERNAME. I am trying to install CRM for
Outlook. The installation is telling me I am "Not a Domain User." It looks
like I am headed down the same path - one day shortly the machine will boot
as DOMAIN\USERNAME.

Clearly I'm not doing something correctly either with the account priviliges
or when I join. I don't want to get this new profile tweaked and then have to
redo it. Could someone please articulate what I am doing incorrectly?

Thanks in advance.
JB