procedure TForm1.Button1Click(Sender: TObject);
var
  i, j: integer;
  buf: array [0..499] of char;
  DrvStr: array [0..9] of char;
  LogDrives: set of 0..25;
begin
  integer(LogDrives) := GetLogicalDrives;
  for i := 0 to 25 do
    if (i in LogDrives) then ListBox1.Items.Add(chr(i + 65));

  GetLogicalDriveStrings(1000, buf);
  i := 0;
  repeat
    FillChar(DrvStr, SizeOf(DrvStr), #0);
    j := 0;
    repeat
      DrvStr[j] := buf[i];
      inc(j);
      inc(i);
    until (buf[i] = #0) or (j > 9);
    inc(i);
    ListBox2.Items.Add(DrvStr);
  until ((buf[i-1] = #0) and (buf[i] = #0)) or (i > 499);
end;