Have you installed the latest version directly from their website?
Version 4.42 ( - CURRENT VERSION - ) (Release date: 2016-03-10)
◾New File menu: Save Selection as (Hotkey: CTRL + SHIFT + B)
◾New option in Capture dialog: Show timer countdown
◾New option in Export Tiles dialog: Extract all pages from multipage files
◾New option in Fine Rotation dialog: Select "best" old image
◾New option in Print dialog: No image overflow on page
◾New HTML-Export dialog option: Copy extra files to destination folder
(prepare a "copy_files.txt" file with filenames)
◾Some PCX/BMP/PPM loading bugs fixed (thanks to Moshe Kaplan)
◾Improved FITS format loading
◾New text pattern: $R = image aspect ratio (width/height)
◾New hotkey: CTRL + Click into selection = clear selection
◾Some minor fixes (Thumbnails/folder scan)
◾Some workarounds for Windows-10 bugs/issues (Installer signature, Associations)
◾Several PlugIns are changed/updated, please install the newest versions
I'm not a developer so my knowledge is pretty limited, however it sounds like maybe they had a problem with their code-signing certificate not too long ago? Who knows, maybe due to recent changes where sha-1 code signing certificates are being deprecated and no longer being valid if timestamped after 1/1/2016 or have no timestamp at all?
If you've uninstalled any older versions of IrfanView and installed the latest version shown above directly from their website (where it seems like they fixed some issues), it maybe something worth taking up directly with InfraView on their forum. I wouldn't disable any features to bypass the "This app has been blocked for your protection" warning dialogue, as it's there to protect users. You need to get to the root cause of why the publisher is not trusted and the first point of call would be to contact IrfanView themselves as their developers should have a greater understanding why their executable is showing the publisher as untrusted.
Just a follow up, for IrfanView 4.41 the code-signing certificate was revoked by their Certificate Authority for some reason. Therefore that certificate can not and should not be trusted again. If you are using IrfanView 4.41, this is why you are getting the warning dialogue saying that the publisher is "Not Trusted".
Last edited by ARC1020; 03 Jul 2016 at 19:04.