I have an Adobe Illustrator CS3 file artboard size A0. Export to jpg cuts off most of the image. How do i fix?

The artboard has nothing to do with where the image is cut off. You can hide it if you want: ';View';, ';Hide Artboard';. The only reason I can think of for your image to be getting cut off would be that maybe you have a crop area in there? To release select ';Object';, ';Crop area';, ';Release';.