Select ``,* from table?
You can do the following:

CREATE TABLE tablename_temp (id int AUTO_INCREMENT PRIMARY KEY)
ENGINE=InnoDB 
SELECT * FROM tablename;

ALTER TABLE b
ADD UNIQUE INDEX some_index_name (your_original_key);


You can find the documentation here: http://dev.mysql.com/doc/refman/5.1/en/create-table-select.html
And a small example on SQLFiddle.