How to focus stack a set of images in Photoshop

I recently rented a Nikon 105mm VR Macro lens for a weekend, and wanted to experiment with different types of macro photography.

One of the things I was most interested in was focus stacking. See, there's a problem with macro photography in that you're dealing with a depth of field measured in millimeters when reproducing images at a 1:1 ratio, even stopped down to f/8 or f/11. And, wanting to avoid diffraction at higher apertures, there's no way to take a straight-out-of-camera picture of a 3D object that's sharp from front to back.

(There's also a video version of this post, embedded below)

"Licensing for this product has stopped working" - Adobe CS3/CS4 on a Mac

Recently, I had to recover my iMac from a Time Machine backup and a hard drive replacement (my old drive flaked out—see how I repaired my hard drive here (video included!)).

Upon trying to open any Adobe Creative Suite 3 app (I use Photoshop and Illustrator daily...), I got the following error window:

Adobe Illustrator - Licensing for this product has stopped working

I was taken to this Adobe Support page, which suggests a variety of options for fixing the problem—all of which didn't work for me.