This is exactly what it sounds like, I put an ADB ball mouse inside of a USB optical mouse case. Pictures are comming but basicly I took apart a broken Apple Pro mouse and noticed that the apple ADB mouse II (the curvy one) had innerds of basicly the same size. I test fitted the main board of the ADB mouse, it was a little big so I ground down the sides until it fit. Nice but there was still no place for the ball to come out and no place for the main board to attach. My solution was to cut a big hole in the bottom of the USB mouse case and cut the ball hole area out of the ADB mouse. I then epoxied the two pieces into one and flatened the seam with two more layers of epoxy. The next part was the clicking, a necessary part of any mouse. To make the clicker work I used some plastic from the USB mouse along with some hot glue. Using the pastic and the glue I made a raised pad so the top of the mouse reaches the clicker on the mouse mainboard. Once all this was done I needed to test the setup, and to my dismay the tracking only worked in three of four directions. When you went right the ball stopped touching the right hand roller. This was happening because the mouse was sitting to low in the case. I started by cutting as much as possible out of the inside of the case, this helped but tracking still sucked. So I sanded the bottom of the mouse down until I had good tracking. Then I went to paint, I chose white for all parts except the cord and the ball retainer ring. I painted in two coats with atleast two weeks inbetween painting. Then I let the parts sit for another two weeks or so and put the mouse together for another test run. The paint on the bottom was just thick enough to messup the tracking again and I didn't want to sand and repaint so I looked for another way around. my solution was to use new, bigger screws to hold the mouse mainboard in place, this moved the board down just enough to make tracking work again. I then epoxied the case shut. I have been "testing" (playing civ1! with) the mouse for about a week and it works great. The only things that aren't perfect are the tracking speed and ease of clicking. The tracking speed is slower than on a unhacked ADB mouse II so you loose a little bit of resoultion, not enough to make text selection hard or anything. The clicking motion is firm (I like that) but a little squishy because I used hot glue on the raiser.
If I were to do it again I'd make everything white, the silver doesn't look as good as I thought it would.