Môžeš sa inšpirovať takto:

procedure TForm1.Button1Click(Sender: TObject);
var
 Drive: Char;
 DriveLetter: String[4];
begin
 for Drive := 'A' to 'Z' do
 begin
  DriveLetter := Drive + ':\';
  case GetDriveType(PChar(Drive + ':\')) of
   DRIVE_REMOVABLE:
    Memo1.Lines.Add(DriveLetter + ' Vymeniteľný Disk (USB,FLoppy)');
   DRIVE_FIXED:
    Memo1.Lines.Add(DriveLetter + ' Pevný disk (HDD)');
   DRIVE_REMOTE:
    Memo1.Lines.Add(DriveLetter + ' Sieťový Disk (Network)');
   DRIVE_CDROM:
    Memo1.Lines.Add(DriveLetter + ' Jednotka CD-ROM (CD/DVD)');
   DRIVE_RAMDISK:
    Memo1.Lines.Add(DriveLetter + ' RAM Disk');
   end;
 end;
end;