I am at school now, on a ****ing linux so I cant test this. However, am I missing something, or do you have to unrar this?? If so, it will be 4 gigs. But here's and idea... Use Windows compression on it and windows might compress it back, and you will still be able to use the image. I do it for all my images. Ill try it when I get home
Its funny, I was working on this same concept, but it looks like BLeH beat me to it :P.