Author: Jonas Bilinkevicius 

Can anyone tell me how to set and reset the Windows TaskBar AlwaysOnTop property 
from within my application?

Answer:

1   procedure TForm1.Button1Click(Sender: TObject);
2   var
3     hw: HWND;
4   begin
5     hw := FindWindow('Shell_TrayWnd', nil);
6     if hw <> 0 then
7     begin
8       if (GetWindowLong(hw, GWL_EXSTYLE) and WS_EX_TOPMOST) <> 0 then
9       begin
10        label1.caption := 'Taskbar is topmost';
11        SetWindowPos(hw, HWND_NOTOPMOST, 0, 0, 0, 0, SWP_NOSIZE or SWP_NOMOVE);
12      end
13      else
14      begin
15        label1.caption := 'Taskbar is not topmost';
16        SetWindowPos(hw, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOSIZE or SWP_NOMOVE);
17      end;
18    end;
19  end;