Use this code to detect the hard disk's serial number:
Thanks to Jonathan Arnett for a corrected version of previously posted code.
uses
SysUtils, Dialogs, Windows;
function HDD_Serial : string;
var
SerialNum : dword;
a, b : dword;
Buffer : array [0..255] of char;
begin
if GetVolumeInformation('c:\', Buffer, SizeOf(Buffer), @SerialNum, a, b, nil, 0) then
Result := IntToHex(SerialNum, 8)
else
Result := '';
end;