Воспользуйтесь функцией SystemParametersInfo(), переслав ей в качестве параметров - SPI_GETWORKAREA и адрес структуры типа TRect, куда будут передан полученный результат.
Пример :

             procedure TForm1.Button1Click(Sender: TObject); 

             var 

               r : TRect; 

             begin 

               SystemParametersInfo(SPI_GETWORKAREA, 

                                    0, 

                                    @r, 

                                    0); 

               Memo1.Lines.Add(IntToStr(r.Top)); 

               Memo1.Lines.Add(IntToStr(r.Left)); 

               Memo1.Lines.Add(IntToStr(r.Bottom)); 

               Memo1.Lines.Add(IntToStr(r.Right)); 

             end; 

Ответ :
Вызовите функцию mciSendCommand (из библиотекиMMSystem) передав ей параметр MCI_SET_DOOR_CLOSED.
Пример :

             uses MMSystem; 

             procedure CloseCD(Drive : char); 

             var 

               mp : TMediaPlayer; 

             begin 

               result := false; 

               Application.ProcessMessages; 

               mp := TMediaPlayer.Create(nil); 

               mp.Visible := false; 

               mp.Parent := Application.MainForm; 

               mp.Shareable := true; 

               mp.DeviceType := dtCDAudio; 

               mp.FileName := Drive + ':'; 

               mp.Open; 

               Application.ProcessMessages; 

               mciSendCommand(mp.DeviceID,  

               MCI_SET, MCI_SET_DOOR_CLOSED, 0); 

               Application.ProcessMessages; 

               mp.Close; 

               Application.ProcessMessages; 

               mp.free; 

               result := true; 

             end; 

             procedure TForm1.Button1Click(Sender: TObject); 

             begin 

               CloseCD('D'); 

             end; 

Вызовите функцию GetDiskFreeSpaceEx(). Возвращаемый функцией результат типа integers конвертируйте в doubles.
Пример :

             function GetDiskFreeSpaceEx(lpDirectoryName: PAnsiChar; 

               var lpFreeBytesAvailableToCaller : Integer; 

               var lpTotalNumberOfBytes: Integer; 

               var lpTotalNumberOfFreeBytes: Integer) : bool; 

               stdcall; 

               external kernel32 

               name 'GetDiskFreeSpaceExA'; 

             procedure GetDiskSizeAvail(TheDrive : PChar; 

                                        var TotalBytes : double; 

                                        var TotalFree : double); 

             var 

               AvailToCall : integer; 

               TheSize : integer; 

               FreeAvail : integer; 

             begin 

               GetDiskFreeSpaceEx(TheDrive, 

                                  AvailToCall, 

                                  TheSize, 

                                  FreeAvail); 

             {$IFOPT Q+} 

              {$DEFINE TURNOVERFLOWON} 

              {$Q-} 

             {$ENDIF} 

               if TheSize >= 0 then 

                 TotalBytes := TheSize else 

               if TheSize = -1 then begin 

                 TotalBytes := $7FFFFFFF; 

                 TotalBytes := TotalBytes * 2; 

                 TotalBytes := TotalBytes + 1; 

               end else 

               begin 

                 TotalBytes := $7FFFFFFF; 

                 TotalBytes := TotalBytes + abs($7FFFFFFF - TheSize); 

               end; 

               if AvailToCall >= 0 then 

                 TotalFree := AvailToCall else 

               if AvailToCall = -1 then begin 

                 TotalFree := $7FFFFFFF; 

                 TotalFree := TotalFree * 2; 

                 TotalFree := TotalFree + 1; 

               end else 

               begin 

                 TotalFree := $7FFFFFFF; 

                 TotalFree := TotalFree + abs($7FFFFFFF - AvailToCall); 

               end; 

             end; 

             procedure TForm1.Button1Click(Sender: TObject); 

             var 

               TotalBytes : double; 

               TotalFree : double; 

             begin 

               GetDiskSizeAvail('C:\', 

                                TotalBytes, 

                                TotalFree); 

               ShowMessage(FloatToStr(TotalBytes)); 

               ShowMessage(FloatToStr(TotalFree)); 

             end; 

Вначале необходимо вызвать функцию FindWindow(), чтобы определить handle TaskBar. Затем вызвите функцию ShowWindow(), передав ей в качестве параметра костанту SW_HIDE.
Пример :

             procedure TForm1.Button1Click(Sender: TObject); 

             var 

               hTaskBar : THandle; 

             begin 

               hTaskbar := FindWindow('Shell_TrayWnd', Nil); 

               ShowWindow(hTaskBar, SW_HIDE); 

             end; 

             procedure TForm1.Button2Click(Sender: TObject); 

             var 

               hTaskBar : THandle; 

             begin 

               hTaskbar := FindWindow('Shell_TrayWnd', Nil); 

               ShowWindow(hTaskBar, SW_SHOWNORMAL); 

             end; 

Воспользуйтесь функцией GetSystemMetrics(), переслав ей флаг SM_NETWORK.
Пример :

             procedure TForm1.Button1Click(Sender: TObject); 

             begin 

               if GetSystemMetrics(SM_NETWORK) AND $01 = $01 then 

                 ShowMessage('Machine is attached to network') else 

                 ShowMessage('Machine is not attached to network'); 

             end;