function MyGetVolumeInfo(DriverLetter : String): TDiskExtent;
Var
  hVolume : THandle;
  DiskExtents : PVolumeDiskExtents;
  dwOutBytes : Cardinal;
  DrvLetter : Char;
begin
  try
    DrvLetter := PChar(UpperCase(DriverLetter))[0];
    With Result do
    begin
      DiskNumber := 0;
      StartingOffset.QuadPart := 0;
      ExtentLength.QuadPart := 0;
    end;
    hVolume := CreateFile(PChar('\\.\' DrvLetter ':'),
                          GENERIC_READ Or GENERIC_WRITE,
                          FILE_SHARE_READ Or FILE_SHARE_WRITE,
                          Nil,
                          OPEN_EXISTING,
                          0,
                          0);
    if hVolume = INVALID_HANDLE_VALUE then Exit;
    DiskExtents := AllocMem(Max_Path);
    if DeviceIoControl(hVolume,
                       IOCTL_VOLUME_GET_VOLUME_DISK_EXTENTS,
                       nil, 0,
                       DiskExtents,
                       Max_Path,
                       dwOutBytes, nil) then
    begin
      if DiskExtents^.NumberOfDiskExtents > 0 then
        Result := DiskExtents^.Extents[0];
    end;
  finally
    FreeMem(DiskExtents);
    CloseHandle(hVolume);
  end;
end;