可以用WMI来获取磁盘及分区编号

{$APPTYPE CONSOLE}

uses
  SysUtils,
  ActiveX,
  ComObj,
  Variants;


function ListDrives : string;
var
  FSWbemLocator  : OLEVariant;
  objWMIService  : OLEVariant;
  colDiskDrives  : OLEVariant;
  colLogicalDisks: OLEVariant;
  colPartitions  : OLEVariant;
  objdiskDrive   : OLEVariant;
  objPartition   : OLEVariant;
  objLogicalDisk : OLEVariant;
  oEnumDiskDrive : IEnumvariant;
  oEnumPartition : IEnumvariant;
  oEnumLogical   : IEnumvariant;
  iValue         : LongWord;
  DeviceID       : string;
begin;
  Result:='';
  FSWbemLocator   := CreateOleObject('WbemScripting.SWbemLocator');
  objWMIService   := FSWbemLocator.ConnectServer('localhost', 'root\CIMV2', '', '');
  colDiskDrives   := objWMIService.ExecQuery('SELECT DeviceID FROM Win32_DiskDrive');
  oEnumDiskDrive  := IUnknown(colDiskDrives._NewEnum) as IEnumVariant;
  while oEnumDiskDrive.Next(1, objdiskDrive, iValue) = 0 do
   begin
      Writeln(Format('DeviceID %s',[string(objdiskDrive.DeviceID)]));
      DeviceID        := StringReplace(objdiskDrive.DeviceID,'\','\\',[rfReplaceAll]);
      colPartitions   := objWMIService.ExecQuery(Format('ASSOCIATORS OF {Win32_DiskDrive.DeviceID="%s"} WHERE AssocClass = Win32_DiskDriveToDiskPartition',[DeviceID]));
      oEnumPartition  := IUnknown(colPartitions._NewEnum) as IEnumVariant;
      while oEnumPartition.Next(1, objPartition, iValue) = 0 do
      begin
       if not VarIsNull(objPartition.DeviceID) then
       begin
        Writeln(Format('   Partition %s',[string(objPartition.DeviceID)]));
        colLogicalDisks := objWMIService.ExecQuery('ASSOCIATORS OF {Win32_DiskPartition.DeviceID="'+VarToStr(objPartition.DeviceID)+'"} WHERE AssocClass = Win32_LogicalDiskToPartition');
        oEnumLogical  := IUnknown(colLogicalDisks._NewEnum) as IEnumVariant;
          while oEnumLogical.Next(1, objLogicalDisk, iValue) = 0 do
          begin
              Writeln(Format('     Logical Disk %s',[string(objLogicalDisk.DeviceID)]));
              objLogicalDisk:=Unassigned;
          end;
       end;
       objPartition:=Unassigned;
      end;
       objdiskDrive:=Unassigned;
   end;
end;

begin
 try
    CoInitialize(nil);
    try
      ListDrives;
    finally
      CoUninitialize;
    end;
 except
    on E:Exception do
        Writeln(E.Classname, ':', E.Message);
  end;
  Readln;
end.