One of my co-workers, in trying to find the install location of Microsoft Word, found a cool little registry tree.  Here is the key:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Applications

Underneath this key, there are keys named Winword.exe, EXCEL.EXE, Outlook.EXE, MSACCESS.EXE, POWERPNT.EXE, explorer.exe, iexplore.exe, AcroRD32.exe, iTunes.exe, javaw.exe, and so on.  It appears many of the big companies use this area to put information about how to do certain commands for a product from a shell (like open, edit, print, etc.).

My next post will be about another section under SOFTWARE\Classes that I discovered.