Here's what I did... pretty much like daveor... what I did was choose select/all, go to edit/free transform. Right click and choose warp, then I warped it to look straight'ish (by warping the horizontal lines... etc)... there were areas that were affected by the warp (a little at the bottom & right side)... I cloned in and replaced (the right side was bowed some, and the bottom slanted a little). Best thing is that it retained your original image aspect/view. It probably needs to be straightened some more... but now that you know how I approached it... you can work on it, and get it exactly how YOU want it
