Microsoft Windows Registry Guide, Second Edition

Appendix A

File Associations

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. I've also added commands to the My Computer object so that I can quickly access Registry Editor (Regedit) and Tweak UI. If you master the contents of HKCR, the opportunities for tweaking Windows so that it looks and feels the way you want are boundless.

The root key HKCR is many times more complex than it was back in the days of Microsoft Windows 95, when I wrote my first registry book. I won't even attempt to describe all the different values you find in HKCR. Instead, I'm going to describe the most useful subkeys and values so that you can customize Windows using the same techniques that I use.