I was doing some playing with Kindle for PC 1.29. Since my original method blocks all writes to that registry key, it does not let Kindle for PC store such things as books opened,etc.
As an alternative (thanks, jhowell!), I did a batch file that kicks off Kindle for PC, waits 10 seconds and then imports the deKFX.reg file. I tried to make the batch file generic by using variables for the Appdata/Local and user home directory. The pause can be removed when you are happy with the timeout setting (basically on my system, the Kindle app opens and then the reg import happens, your system may need a higher number depending on system speed). Both the kindle.cmd and deKFX.reg files were placed on my desktop.
kindle.cmd
Code:
start %LOCALAPPDATA%\Amazon\Kindle\application\kindle.exe
timeout 10
reg import %HOMEPATH%\Desktop\deKFX.reg
pause
deKFX.reg
Code:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\SOFTWARE\Amazon\Kindle\User Settings]
"isKRFDRendererSupported"="false"
Both files are in the .zip file attached to this message. Unpack to your desktop and check if it works for you.