ALT+TAB, CTRL+ESC, CTRL+ALT+DEL
{If you wish to disable those keys while your
application is running call SystemKeys:
When you call SystemKeys, if Disable is True,
the keys will be disabled, False otherwise.}
procedure SystemKeys(Disable: Boolean);
var OldVal : LongInt;
begin
SystemParametersInfo(SPI_SCREENSAVERRUNNING,
Word(Disable), @OldVal, 0);
end;