For basic Photoshopping you would probably do just fine with the latest version of Photoshop Elements which is basically a stripped down version of Photoshop but is much cheaper and easier to use and, from what I've read, more than adequate for the average consumer. I don't know how much you can do with Elements but it should be good enough for most basic photo editing work, if you want to get into serious retouching, restoration, and compositing work then you'd almost certainly need a full copy of Photoshop which I think is CS4. Be forewarned but that the regular edition of Photoshop will cost you several hundred dollars unless you can either qualify for an educational discount (teacher or student) or acquire through alternative means in which case it will cost you a whole lot less.