CTRL ALT DEL block

I need to block the CTRL ALT DEL keys, i tried 3 way to block it but
unsuccefull

1) i tried changing the policie
HKEY_CU/Software/Micrsoft/Windows/CurrentVersion/Policies/DisableTaskMgr  1

But doesn't word under a windows restricted user

2) i tried SystemParametersInfo(SPI_SETSCREENSAVEACTIVE, 1, nil, 0)

But only works under Win 9x

3) i tried also intercepting the pressed keys with:

     SetWindowsHookEx(hookKeyboard,
                                   @LowLevelKeyboardProc,
                                   System.MainInstance,
                                   $0);

But doesn't work with CTRL ALT DEL combinations.

ARE THERE AN OHTER WAY TO BLOCK THOSE KEYS COMBINATION UNDER WINDOWS XP /
VISTA ?

Thanks in advance.