Irfanview won't associate with NEF files

[idamtnboy]

I have all the plugins installed, and NEF is in the list of of files when I load default extensions. NEF is not in the drop down list of file extensions. Windows 10 absolutely will set an association between NEF and Irfanview. I can set the association to Paint Shop Pro with no problem, but I cannot change it to Irfanview. I even deleted all the associations to NEF in the registry and still Irfanview won't associate. What's the problem?

[Bhikkhu Pesala]

I was able to associate NEF files with IrfanView (I chose the 64-bit version) by double-clicking a NEF file in Windows Explorer and choosing IrfanView 64-bit from the list of programs when I selected more apps.