procedure TForm1.Button1Click(Sender: TObject);
var
ld : DWORD;
i : integer;
begin
ld := GetLogicalDrives;
for i := 0 to 25 do begin
if (ld and (1 shl i)) <> 0 then
Memo1.Lines.Add(Char(Ord('A') + i) + ':\');
end;
end;