Como Maximizar un FORM?

[eddg]

>> boton 1 = toolbutton20
>> boton 2 = toolbutton16

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procedure Tprincipal.ToolButton20Click(Sender: TObject);
begin
toolbutton16.Visible:=true;
toolbutton20.Visible:=false;
principal.BorderStyle:=bsnone;
end;


procedure Tprincipal.ToolButton16Click(Sender: TObject);
begin
principal.BorderStyle:=bssizeable;
toolbutton16.Visible:=false;
toolbutton20.Visible:=true;
end;


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http://img149.imagevenue.com/img.php..._123_635lo.jpg

Me aparece este error:
[Warning] Unit1.pas(8): Unit 'ShellCtrls' is specific to a platform
[Warning] Unit1.pas(8): Unit 'Outline' is deprecated