I think !MiKrofT alluded to the fact it's not plainly viewable when he said it's encrypted in the registry. I don't believe of any way to do it without using any external software.
I usually use
Magical Jellybean if I want to find a serial. The one I linked doesn't require an installer and works for most of the MS products. (although apparently doesn't work for Office 2010)
If you're really paranoid about it sending off your key, then you can always just disconnect the network cable (or turn off WiFi) when you run the application to prevent it sending anything out. If you're REALLY paranoid, then run it inside a sandbox and clear it out when you're done before you reconnect your network.