I can't speak for PS 7, but for PS 6, when you select a tool, there's a littled botton on the upper right of the toolbar. Pressing it brings a drop down list of what can be selected for pressure sensitivity, for the brush for example, yoiu have three choices, them being Opacity, brush size, and color (which goes from the forground to the background colour gradually depending on your pressure you put). Where it would be located in PS7, I'm unsure, but if it's anything like PS 6, which me thinks it is, it should be on the bar below the bar containing FILE, EDIT, Layers, Windows, etc.