This is the perspective correction screen from the PSCS2 Lens correction Filter.
Use this as a guide for the Transform>perspective in PS7
Note that the horizontal correction has equal amounts at top and bottom.
The vertical correction is applied in proportion to the image aspect ratio.
(In this case about 3:2, compressed at bottom and lost at the top)
This bears out by overlaying a circle in the center of the picture and then
transforming to retain a good centered circle while straightening vertical lines.
See next image.