Basically, you need to remove the fields the game you're converting to doesn't use and add the fields it requires. Not the most challenging of tasks but a bit fiddly if you're not familiar with the databases.
It's possible, but it's a lengthy process and one I would not recommend if you're a novice with DBF editing. Basically, it involves adding the fields to the 06 database so that all the values NBA Live 08 uses are present, along with correcting dunk packages and the like.