Harddrive replacement and login

Hi All,
I have a macbook pro mid 2010. I put a SSD in the optical drive which I use to run all my applications and put the OS Lion on there too. I ran out of space on my original Mac HD so I tried to replace it with a 750 GB Momentus HD.

I cloned the Mac HD to the Momentus in an external drive using Carbon Copier and then swapped into the macbook. I couldn't login, it said something about not being able to find user "my_name". With the Mac HD in the external drive, I can log in no problem and it show the momentus as device, not an internal drive.

I since swapped them back and created an admin login for the SSD...no problem, I can log in but that doesn't show my files. Can I login through the SSD and make a third admin to the Momentus Harddrive?

How would I do this swap properly.

Thanks!