Whenever I want to attach something, it is not a supported file type. For example, if I want to attach and POV-ray picture, its says it does not support BMP. How do I change it to jpg or some other supportable file type?

you need to use a program like The GIMP, Paint Shop Pro or Photoshop to save an image as a jpg

Or, like, Paint. But that's pretty hard to come by.