> So I guess our steam > library > M&B (games) > CD Key...
> ... will not work on the reclaim page?
No, most likely it won't work that way.
But there might be a different method to get a DRM free version of the game:
1) Install the steam version of the game
2) Eyport the registry key at:
3) Delete the steam version
4) Download the trial version of Warband from:
5) Install the trial version
6) Switch the trial version to full mode by adding the above registry key
(Double-click on the .reg file)
If you want to keep the steam version, then you only need to do 1), 4)