Two identical users at login, not under user accounts. Vista Home

I have a similar issue. I have a customer with new Dell C521 with Vistal
Home. In trying to get peer-to-peer sharing setup I have managed to get the
user name twice, one with a known password, and the other with an unknown
password.
Set up regestry for autologon with the known password, but on startup, a
message "invalid password". I have to SWITCH User to get the other user with
the same name. When I click it and enter password (same as in registry), it
starts up.
In user accounts, only one user shows up. Changing that user password to
the known value does not help>

Winford