Don't use the registry! Access to the registry has been restricted since it was first introduced, and the restrictions are likely to get more heavy duty rather than less - due to programs overusing it, and security concerns in the same way that it is harder and harder to store your data files and config info in the application installation folder.
Instead store a file in a sensible place that you will have access to. This can help:
Where should I store my data?[
^]