PictureCode no longer issues replacement keys. If you lost your serial, consider the plugin abandonware — legally gray but practically unrecoverable. The ethical path is to transition to one of the modern alternatives listed above.
This article provides an in-depth look at the features, installation, and usage of the Noise Ninja 2.4.2 plugin, as well as addressing the search for its activation, including keygens and serial numbers, for older, legacy systems. What is Noise Ninja 2.4.2? PictureCode no longer issues replacement keys