Customizing Windows Explorer Context menu

Ever wondered how does the right click menu (which is actually a context menu) work ? For example, when I right click in windows explorer, I see an option which says "open command window here". Do You know why I see this ? Well I see this because I have following entries in my registry. [HKEY_CLASSES_ROOT\\Drive\\shell\\cmd]
@="Open Command Window Here"
[HKEY_CLASSES_ROOT\\Drive\\shell\\cmd\\command]
@="C:\\WINDOWS\\System32\\cmd.exe /k cd "%1""
If You have never used a tweaking utility and have newly installed Windows XP, You would not see this option. You would have to navigate to [[HKEY_CLASSES_ROOT\\Drive] go and create two subkeys ("cmd" and within that "command" and would have to put the text "Open Command Window Here" without quotes in default string value of "cmd" key and the text "C:\\WINDOWS\\System32\\cmd.exe /k CD"%1"" without quotes in default string value of command key). After this You need to REBOOT for these changes to take effect.
Trick is in adding similar entries for other applications as well even though its much harder to come with ideas about what to put in the context menu!!!! .