This is a well-written batch file driven backup and restore, so it writes nothing to your system. Registry keeps deleted data too. The data remains in registry but it is not visible to you. So we use regedit to export only visible data and than rebuild registry from that data. If not download it from Microsoft.
Regclean cleans registry from all the trash, dead links etc.
Run regclean and have it clean all the errors it can find. That will import all the changes back to the registry. Here is a safe technique that can reduce the size of the Registry up to 10 percent. Make a backup of your system and especially the current Registry. Restart Windows in an MS-DOS Mode session.