I had this recurring thing where Irfanview would get stuck on the last file type I saved an image as. E.g. if I chose to save as .ico (just for that one time around, Irfanview would keep remembering that. I suppose that’s handy for some things, but I want .jpg as the default, w/o me having to change it manually each time.

I found a couple of items, one or both of which might be enough, that is if you’re having the same problem. Look for i_view32.ini on your system, then look for this section:

[Save]
ViewMode=28751