A script or a program can be added to the context menu by editting the registry

1. add the text to display
   Create a new regustry key under the path:
   HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\MenuExt
   The text can include an ampersand (&) character, which will cause the character that follows to be underlined and used as a shortcut key.


2. Define the script that should be run
   Set the default value of the key to the URL of the page that contains the script you want the context menu entry to execute. This script can obtain the parent window object, the screen where the context menu item was executed, from the menuArguments property of the external object.
   
   
3. define the context the menu item should show up in by adding the key "Contexts" under the key for the menu text. For example:

HKCU\Software\Microsoft\Internet Explorer\MenuExt\<Menu Text>\Contexts
The value of Contexts is a bit mask of the following values:


Context	Value
Default	0x1
Images	0x2
Controls	0x4
Tables	0x8
Text selection	0x10
Anchor	0x20

A note to programmers:Setting the value of the context to 0x1 makes the script run as if it had been called with the "showModalDialog" method. References http://msdn2.microsoft.com/en-us/library/aa753589(VS.85).aspx