If you're trying to remove an entry from the IE context menu, run regedit
and navigate to this key:
[HKEY_CURRENT_USER\Software\Microsoft\ Internet Explorer\ MenuExt]
Your entry will be a subkey of that key. Select the MenuExt key and export
it (just to be safe) Then select the unwanted subkey and delete it.
I don't know how to add an item to the context menu.
Regards,
Don