NPMOD32.DLL is a legacy Windows development library file created by Olivier Lapicque in the late 1990s and included in his ModPlugin browser addon. It was designed to play older module music files which were popular with the demo and music scenes.
Sometimes programmers would forget to include this file when packaging their applications. That later lead to the missing NPMOD32.DLL error notice.
To fix this error download and copy NPMOD32.DLL into the same directory as the application requesting it.