1) Probably not legally. Only Gateway could sell them, and they wouldn't, since they would want you to buy a whole new computer.
2) Such a thing probably could not be made for general use. The problem is that the installation loads drivers specific to the motherboard and whatever devices may be on it. So an installation for one model of Gateway machine probably would not work on another model.
So I guess that you have to buy a Win7 disk and do a fresh install. When did you buy the machine from Gateway; if you are upgrading from XP you may be entitled to an upgrade disk. If you are trying to deal with a dead drive, Gateway can at least provide recovery discs specific to your model of computer. Which describes your case?
Edit: Egads, that's a nine-year-old model. You may find it awfully slow for Win7.