Identifies a currently open key in the registry or any of the following predefined reserved handle values:
Points to a null-terminated string containing the name of the subkey with which a value is associated. This parameter can be null or a pointer to an empty string. If the parameter is NULL, the value will be added to the key identified by the hKeyRoot parameter.
Points to a string containing the name of the value to retrieve. If a value with this name is not already present in the key, the function adds it to the key.