Como obter o numero de serie do hd

Function TForm1.SerialNum(FDrive:String) :String;
var
Serial: DWord;
DirLen, Flags: DWord;
DLabel : Array[0..11] of Char;
begin
Try
GetVolumeInformation(PChar(FDrive+':'),dLabel,12,@Serial,DirLen,Flags,nil,0);
Result := IntToHex(Serial,8);
Except
Result := '';
end;
end;