Prova con questo script:

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);
end;