One option is to remove the standard menu along with the icon and draw the
icon and menu on your own, but it'll not change the menu when you
right-click the window's button in the taskbar. An other possibility is to
use shell functions to add extra menu items to your form's system menu, and
these changes will be visible in both the titlebar and taskbar; I don't know
if you can remove items this way.

You can modify the appearance and remove and add menuitems to the Window
Menu, but you'll need to do it via Interop.
Theres a basic Window Menu manipulation example on my site:
http://dotnetrix.co.uk/menus.html