how to add new items to certain file extension context menu (to .mp3 files for instance)
I've also noticed that there is common items in all context menus across the windows, does they all share/inherit one context menu ? where is it : which one is for text
what such keys are called and how to generate them (for instance {11dbb47c-a525-400b-9e80-a54615a090c0})
also is there a good brief reference for the registry that you would recommend ?
Type regedit in RUN dialog box or Start Menu searchbox and press Enter. It'll open Registry Editor, now go to following keys:
HKEY_CLASSES_ROOT* (for adding an option in All files context menu) HKEY_CLASSES_ROOT\Directory (for adding an option in folders context menu only) HKEY_CLASSES_ROOT\Drive (for adding an option in Drives context menu only) HKEY_CLASSES_ROOT\Unknown (for adding an option in unknown files context menu)
Now under the above mentioned keys, you'll find "Shell" and "Shellex" keys. Both keys contain various entries, which are displayed when you right-click on a file, folder or drive. We'll use "Shell" key in this example:
%programfiles%\Winamp\winamp.exe.A full reference to this can be found here
how to add new items to certain file extension context menu
How you massage the registry to create context menu item entries is already covered by this MSDN article. It is extensive and well done, no need to repeat it here.
I've also noticed that there is common items in all context menus across the windows
The majority of them are baked-in items that Explorer itself understands. There is a backdoor to add an item yourself to any file, the HKCR\* registry key is used. Use this sparingly, it is pretty annoying to users.
for instance {11dbb47c-a525-400b-9e80-a54615a090c0}
That's an example of a custom shell extension handler, you found this one back in the HKCR\Folder registry key, the key that adds items to any directory. Think of it as a plug-in that adds capabilities to Explorer that it doesn't have itself. The {guid} selects the executable file that Explorer loads to implement the item. Navigate to HKCR\Classes\CLSID\{guid} to see that file, you'll see it is implemented by c:\windows\system32\explorerframe.dll
Writing your own shell extension handler is not that easy, it requires COM coding skills in C++. A coding technique that is getting obscure. Using something like C# is technically possible but strongly discouraged by Microsoft and they won't support it. You need to write an in-process COM server that implements the IContextMenu interface. Programming guide is here.
