NI has not exposed in the Programmer's toolbox the functions for deleting keys or values in the registruy. They are indeed included in Windows APIs, to which toolbox functions ultimately rely on, as you can see looking at RegXXX functions in toolbox.c
The functions you are to use are RegDeleteKey and RegDeleteValue that are described in Windows SDK accessible from CVI Help menu.
A general warning is that manipulating the registry can turn the machine into unstable state: this is particularly true when deleting values and keys.
