Good afternoon and thank you for posting in the Final Fantasy XIV Technical Support Forums

The Steam and Windows versions of Final Fantasy XIV are incompatible with each other as they are treated as two separate PC platforms. If the Steam version is already registered to the SQUARE ENIX ID, the Windows code cannot be added as the system will not accept the registration code.

As this issue is not a technical concern, this thread will be moved to "General Discussion"

Thank you for visiting the Final Fantasy XIV Technical Support Forums