Pros of config file:
- Easy to do. Don’t need to know any Windows API calls. You just need to know the file I/O interface of your programming language.
- Portable. If you port your application to another OS, you don’t need to change your settings format.
- User-editable. The user can edit the config file outside of the program executing.
Pros of registry:
- Secure. The user can’t accidentally delete the config file or corrupt the data unless he/she knows about regedit. And then the user is just asking for trouble.
- I’m no expert Windows programmer, but I’m sure that using the registry makes it easier to do other Windows-specific things (user-specific settings, network administration stuff like group policy, or whatever else).
If you just need a simple way to store config information, I would recommend a config file, using INI or XML as the format. I suggest using the registry only if there is something specific you want to get out of using the registry.