If you have the software on your PC, but you still can't open the file, you may get in touch with the software developer of that file type. For example, if you know that you have GBC files, you will be able to Google to find out which software packages use the GBC file extension.
If that still does not work, you may have to contact the developer for more guidance. If you don't have the matching software, you will have to download it. Once you know the type of content the GBC file contains (graphics, media, text), you can add the file extension to the default file associations in the computer's settings and try to open it again.
