Microsoft® Windows® Registry Guide, 2nd Edition

Appendix A. File Associations

In this appendix:

Merge Algorithm

File Extension Keys

Program Class Keys

Specialized Keys

COM Class Keys

The bulk of the registry’s content is in HKCR, which is where Microsoft Windows XP and Windows Server 2003 (Windows) store file associations and class registrations. These settings associate different types of files with the programs that can open, edit, and print them. They also register different program classes so that Windows can create objects using them.

A large number of the customizations I make on a regular basis are simple ones in HKCR. For example, I like to add commands to the file association for folders so that I can open a command prompt window with the selected folder set as the current working directory. ...