Further below Isthmis said that once logged into the new site you could change your password to your old one or anything you like.
This may not be completely true, I logged in using the link in the original post and the passwrd sent in an e-mail. When I went into my profile to change my password it wouuld not let me use the old one. It said there was an 8 character minimum and my old one was only 7 characters so it wouldn't let me use it. I had to change it to something different with more characters.
Or did I do something incorrectly?
I had problem too with registration. When I used my old user name and email address, it was saying this user name and email address is being used by another user (its actually me)
Then I changed the user name a bit and used another email address to register successfully.