The 32-bit activation code is provided by 3rd party resellers or retailers of Nero.
The code could be used for unlocking Nero software and bundling the software with the logged in Nero Account. See this article: https://support.nero.com/en/support/solutions/articles/44001820157-i-have-bought-nero-and-got-the-32-bit-activation-code-how-can-i-unlock-my-product-after-installation-
Once the code is used, the Nero software is bundled with the Nero Account. The activation code could not be used anymore.
After reinstalling Nero software, you only have to log in your Nero Account to unlock the software.
You don't need to enter the activation code anymore.