Hit the Windows Key and R, which will bring up a Run... window.
Then type "regedit" in that window and press enter.
Once there, navigate the tree to the location I indicated:
Caba`drin 说:
HKEY_CurrentUser->Software->MountAndBladeWarbandKeys
On the right hand side you should see a list of things like serial_key and activation code. Double click on those two and delete everything in the "Value Data" box. (You may wish to copy their contents to Notepad first, just in case.) Once you have deleted the values, close the Registry Editor and try to run Warband. It should prompt you for your keys now.