Getting a key from the internet is rather risky. They often contain a trojan which you won't know about until it activates. Unless you have the exact right version they won't work anyway.
If you registered Word when you got it, simply ring Microsoft and they should be able to tell you instantly what programs are registered against your name and provide you with a key - if correctly registered.
Did you really have the key of Word on the back of your case? I note you downloaded the prog.