Vista Upgrade Difficulties: User Profile Service failed Logon

I attempted to update my XP Media Center version to Vista Home Premium. I
did an Update not a clean install. The update process was slow, but seemed
to be going well. It got towards the end (I thought) and asked me to confirm
things like my clock but when it went to logon I received the following
messages, "The User Profile Service service failed the logon. User profile
cannot be loaded."

I have not been able to logon to my computer for a week now (am writing this
from work). I contacted Microsoft Support and we spoke on the phone for
30-45 minutes but to no avail. They gave me a case number. However, there
was miscommunication between the tech person and myself and now it's up to me
to call Microsoft back at my convenience.

Before I make that call, I am hoping someone out there can help me or give
me some ideas to try when I get home tonight. I would love to be able to fix
this without starting over.

-Sandra