Who sells a 5x5 key (and what is that?) The only thing I can find from vendors - Amazon, Best Buy, Provantage, etc are keys for online install. To get a DVD key from that, you have to register an Email address, then click "DVD product key". That process is ephemeral, when it even works. Often it says "Activation Server unavailable try later", but it never works again for that Email address. Those Email accounts and Office registrations are promptly deleted, so woe to me if I lose a DVD key.
Also, Microsoft no longer sells Office 2010 at any price, which would be a solution to my problem.