heres a picture of mine. i use ps 7.0

the image menu is open and the "Image Size" is whats highlighted in gray. if i click that Image Size option, it brings up the Image Size box that is shown. notice i got that width set to 500 pixels, not inches. same with height. right below that, you can see that 500 pixels by 200 pixels equals out to about 6.9 x 2.7 inches. a lot different than 500 by 200 inches. that is so much work for the computer to even mess with something like that, it just freezes or shuts down or something, unless you are working with some amazing super computer or somethnig. just remember to change them inches to pixels. also, maybe try changing the resolution to 72 pixels per inch, instead of 300. that might be better too, but i know your main prob is just the inches thing.