[PDF] File Extensions Hive saves registry keys and values of the reference between applications. For example, you can open a link in MS Word. Functions such as this are saved in File Extensions Hive. Sometimes the file extensions are invalid. This problem can be solved by registry repair.
Font Entries are used for font reference on Windows. It won’t have registry errors unless you have installed too many 3rd-party fonts to your computer.
Help Section is used for storing registry keys and values of Windows help file.
File Associations are used for storing registry keys and values of applications reference. Invalid File Associations are definitely registry errors which should be removed.