A question for starcraft 2 owners

My friend asked me to reformat his laptop but he has lost his cd key. He bought it in a store so its the box version not online. If I reformat his computer can he still log into his battlenet account and get his serial or make it work? i heard it ties your cd to your account.
Answer #1
Once you add the game to your battle.net account,
You don’t need your cd key, just your login information.