Ever used this?

http://www.irfanview.com/

I've been using this for years, and it's great B)

the whole program (one free-standing .exe file) is just 850k, so you can fit it on a floppy disk, it can run slideshows, apply certain effects, resize images and all sorts of other stuff!

and if you install the plugins, you can use it as a (admittedly rather naff) movie viewer, as well as support for just about every image format going.

OK, there's better programs out there, but I find it's perfect for doing simple stuff like viewing images (duh!), quick resizes, etc, without having to muck around with PSP and so on.