Welcome to the forum.
I have run into a few sites like that. I think the images are only stored at the site in the bitmap (.bmp) format, and will download as that.
What I do is download it anyway, then after downloading I load the images up in my photo editor (should be a default program that comes with Windows). Once it is in the photo editor, then you can do a 'Save As' and you can select the type of file you want (.jpg).
.jpg of course will save much disk space over the .bmp format. This works for me.
DenverDon

