If you are using the latest version of CVI (5.5), then there are functions in the Programmer's Toolbox (cvi\toolslib\toolbox\toolbox.fp) for reading and writing to the registry. If you aren't using CVI 5.5, you will have to use Windows SDK functions.
In windows SDK that ships with CVI there is a complete chapter about the registry (Win32/Overviews/System Services/Registry). In it there is an exhaustive discussion about reading a writing to it and an example ('Using the registry' item) the you can use as a starting point for you to study. In winerror.h you will fine a listing of errors reported by functions: search in it with 'registry'. Roberto