I am working on web browser only kiosk environment with touchscreen windows 8. I found it better to have only firefox or chrome to run and not explorer.exe because I am unable to disable touchscreen's charms bar.   

I tried to edit `HKEY_LOCAL_MACHINE -> Software -> Microsoft -> Windows NT -> CurrentVersion -> Winlogon` Shell to **firefox.exe** but only black screen shows up.

I tried to edit with notepad.exe and that worked. What do I need to edit shell to have it start firefox but not explorer.exe?