CD key help

Ok guys so a friend mine gave me Guild Wars Factions cause he wasnt into the game and didnt really like it. So he gave it to me cause i play prophicies all the time. The problem is when i go to enter in the cd key it tells me that its already in use. He said he uninstalled the game. Is there something else he needs to do before im able to use the cd key?? Thx

He associated the key with the account he created. Uninstalling it on his computer doesn't make a difference, the key is permanently attached to the account he created. If you ask him for the account name and password you can then play his account; you will never be able to merge it with your existing account.