AVRDUDESS.
Connect up the devices and connect the programming board to the PC USB port. Check the COM port number of the ISP in the Arduino ISP TOOLS>PORT.
Using Windows explorer, navigate to the AVRDUDESS install folder and launch the application. In the Programmer drop down, select Arduino as the programming interface. Select the correct COM port from its drop down. Type in the baud rate, 19200 is the default for the ISP. At the top righthand side select the MEGA2560 in the 2 device boxes. This is sufficient information for avrdudess to read your device settings. Click on READ fuses. The program responds in the DOS window, and updates the fuse readings in the GUI. Clicking on CONFIG will allow you to see the individual fuse settings in bit patterns. They can be modified in this screen.
The default hfuse bit pattern is 110110001 = 0xD8
The NEW lfuse bit pattern is 10100000 = 0xC0
Exit the screen. Then write to the device by clicking WRITE in the fuses section.
Avrdudess reports the changes. Clicking on SAVE will remember your settings.