retornando o papel de parede....

procedure TForm1.Button1Click(Sender: TObject);
var
  Reg: TRegistry;
  s: string;
begin
  Reg := TRegistry.Create;
  try
    reg.RootKey := HKEY_CURRENT_USER;
    Reg.OpenKeyReadOnly (´Control Panel\Desktop´);
    s := Reg.ReadString (´Wallpaper´);
    if s = ´´ then
      ShowMessage (´Nenhum papel de parede definido´)
    else
      ShowMessage (s);
    Reg.CloseKey;
  finally
    Reg.Free;
  end;
end;