Re-assign driver on Azteeg board

I have an Azteeg X3 Pro controller operating a RepRapPro Mendel Tri-color 3d printer. I was having trouble with the z-axis drive and was in the process of adjusting the speeds when I inadvertently installed the SD8825 driver upside down and powered it up. When I corrected the error and installed the driver properly I find that the z-axis does not move - no sound or motion. I have tried the following...

1) installed a different SD8825 driver from a working axis - no effect

2) checked the voltage setting on the driver (still .7 volts)

3) installed a new motor on the z-axis (no effect)

4) checked to see if any fuses blown (none)

5) checked operation of the x and y axis drives (work properly)

I do not plan to use the E4 or E5 drives on this board. If the existing z-axis drive is damaged beyond repair, can I substitute one of these extra drives? How do I set up the board to make this change? I'm using Arduino Configuration H to set parameters. Do I need to reassign the drive via this file?

Thanks in advance for your support.

Gonetotx