Detectando o numero serial do hd

Function 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;