function GetNumberOfCDDrives: Byte;
 var
  drivemap, mask: DWORD;
  i: integer;
  root: string;
 begin
  Result := 0;
  root := 'A:\';
  drivemap := GetLogicalDrives;
  mask := 1;
  for i := 1 to 32 do
  begin
  if (mask and drivemap) <> 0 then
  if GetDriveType(PChar(root)) = DRIVE_CDROM then
  begin
  Inc(Result);
  end;
  mask := mask shl 1;
  Inc(root[1]);
  end;
 end;
 procedure TForm1.Button1Click(Sender: TObject);
 begin
  Label1.Caption := IntToStr(GetNumCDDrives);
 end;