Yes, I'm aware of Belarc, and that works well with XP - Vista, I don't know. But Windows 7 licensing is REALLY complex, compared to earlier versions. And you can't mix an OEM key with non-OEM installation media. And it gets even more complicated when you add additional computers. Once you get to a certain point, you can get volume licensing, but you need at least a minimum number of 2008 servers and/or Windows 7 workstations. Either way, they "check in with home" on a regular basis.
I’d just call Microsoft and see what they say. They have been good to me in other situations.
True, but you CAN mix an OEM key with an UPGRADE media. I did that on the computer I'm typing this reply on. ;-)
The Windows 7 Keyfinder link I posted above finds the Win7 Product Key. You can also use a Win 7 Product Key CHANGER to insert the key, irrespective of the installation media being OEM, Full Install, or Upgrade media. Google "Windows 7 Product Key Changer" to find it.