Need help making a backup game

Hi i have a game called grand turismo 4 and it has a bad scatch on it and i am trying to make a backup for it. I have a dvd decryptor and made a image for gt4. But the file is 5.1 gb and its too big to put on a dvd-r. So i tried to compress it but i dont know what to do after that. Does anybody know, thanks the help i appreciate it.