Windows 8 Upgrade Question

To install the Windows 8 pro upgrade edition, am I actually going to need to input a product key or will it simply recognize the OS I'm running? You see, I'm running Windows 8 RP and haven't actually ever owned a Windows product key.

I'm talking about this version.

The amazon page doesn't actually say anything about a product key but it does say that I need to have one of the listed versions which includes the RP so it's not really very clear.

If I am eligible, I'll damned well preorder this right now.