It looks like IrfanView started recently to depend on SetDllDirectoryW in KERNEL32.DLL. This breaks compatibility with Windows 2000 and possibly other OSes. Disabling it this way https://www.youtube.com/watch?v=HazPWRqSOLU makes IrfanView work again, so I assume it's not essential. While I'm aware Windows 2000 is not supported, it makes life easier for those few people who use IrfanView on their vintage systems.