procedure TForm1.Button1Click(Sender: TObject);
var
 VolumeSerialNumber : DWORD;
 MaximumComponentLength : DWORD;
 FileSystemFlags : DWORD;
 SerialNumber : string;
begin
 GetVolumeInformation('C:\', nil, 0, @VolumeSerialNumber, 
 MaximumComponentLength, FileSystemFlags, nil, 0);
 SerialNumber := IntToHex(HiWord(VolumeSerialNumber), 4) +
 '-' + IntToHex(LoWord(VolumeSerialNumber), 4);
 Memo1.Lines.Add(SerialNumber);
end;