Use ALT FN F4 in Windows 8 and ALT F4 in Windows 7, Windows 10 to close PTBooth App
Hold down ALT and Press F4 in Windows 7, Windows 10

Hold down ALT and Press FN and then F4 in Windows 8

Use "Hot Button" to close PTBooth App

PTBooth will close.
PLEASE NOTE! the "Hot Button" will function only if there are no errors present.