[kh99]

I can't tell you exactly what to do without seeing what your account_data table looks like, but I think you'd just want something like:

INSERT INTO account_data (username, password, email)
	SELECT username, password, email FROM user

(of course you'd have to change the field names and add a table prefix to "user", if necessary).

If you already have an existing table with usernames you might have to do something different.

ETA: also, I guess this doesn't work if the new table is in a different database. I don't know how to handle that off the top of my head.