Double entry in user list

When Vista opened for the first time, there were two listings of Thomas, one
of George and one guest. Since I am the Thomas, I clicked on my name and was
told to enter a PW, which I did...it got me into the program. But, using the
same start up page, clicking on the other Thomas coes not require a PS. "Why
not eliminate one," you ask? When I go to the users accounts, there is only
one that is listed, and that has administrative. I would like to get rid of
one of the Thomas's but not delete all of the settings that were transferred
over from XP after 5 yrs of use. BTW, there is only one listing of Thomas in
the users folder under Thomas's folder, but then it is my whole name, not
just Thomas.
How do I eliminate one of the names?
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tct@usa.com