Create a new project, arrange one Button and Memo in Form1, and write the following code in Button1's onClick event:
procedure TForm1.Button1Click(Sender: TObject);
var
hCurrentWindow: HWnd;
szText: array[0..254] of char;
Begin
hCurrentWindow := GetWindow(Handle, GW_HWNDFIRST);
while hCurrentWindow <> 0 do
Begin
if GetWindowText(hCurrentWindow, @szText, 255)>0 then
Memo1.Lines.Add(StrPas(@szText));
hCurrentWindow:=GetWindow(hCurrentWindow, GW_HWNDNEXT);
end;
end;