Firstly, you should't copy database by copying datafiles. This is a mysql trick that once again proves how crap mysql is.
Use mysqldump to create a proper backup of your data, and restore that backup on your target machine.
As for your current problem, did you stop the source mysql server before you copied the files, and did you stop the target server before you added the files? If not, try again but stop the servers before you copy/insert the files.
A forum, a FAQ, email notification, what else do you need?