This is embarrassing, but I need help

figuring out how to configure Firefox in Windows XP so that I can simply download pictures as .jpgs, etc.
Currently, my Firefox is downloading all images as Paint Shop Pro files (I have PSP loaded on the computer) and it is really irritating to have to convert the images.
I tried the Mozilla help pages, but I can't make heads or tails of what they recommend.
Do I need a plug in of some sort? I looked in the Tools > Options > Manage downloads and that only gives me the option of where to save, not the format or file type.