[dba-SQLServer] Changing database ownership

I have another piece of SQL Server that I do not understand.  I generally
work from my laptop (M90). I open SQL Server and create a database out on
one of my servers.  I had two servers at the time, but I am down to one now.
At the time I was creating a lot of the databases on server AZUL.  Azul's
motherboard died and I moved the databases off to server Stonehenge.  When I
try to attach the databases I get an error something to the effect "cannot
attach because the user M90.jwcolby is not available".  Obviously
m90.jwcolby is my user on my laptop, but why doesn't it just ask me for my
username / password or something?  And how do I change the ownership to
Stonehenge.user or something like that?  Do I even want to do so?

To make matters even stranger, the attach works!  So I am able to continue
truckin on but it is just one of those "panic moments" when I think that I
am going to be locked out of my database.

Does anyone have an English language explanation of what is happening, why,
and how to cause it to go away?

John W. Colby
Colby Consulting
www.ColbyConsulting.com