레코드를 하나 정의하구요..
<!--CodeS-->
USER_INFO_1 = record
    usri1_name: LPWSTR;
    usri1_password: LPWSTR;
    usri1_password_age: DWORD;
    usri1_priv: DWORD;
    usri1_home_dir: LPWSTR;
    usri1_comment: LPWSTR;
    usri1_flags: DWORD;
    usri1_script_path: LPWSTR;
  end;
  lpUSER_INFO_1 = ^USER_INFO_1;
<!--CodeE-->

외부 DLL을 로드합니다.
<!--CodeS-->
  function NetUserEnum(ServerName: PWideChar; Level, Filter: DWORD; var Buffer: Pointer; PrefMaxLen: DWORD; var EntriesRead, TotalEntries, ResumeHandle: DWORD): Longword; stdcall; external 'netapi32.dll';
  function NetApiBufferFree(pBuffer: PByte): Longint; stdcall; external 'netapi32.dll';
<!--CodeE-->

버튼과 리스트박스가 폼 위에 하나씩 있을때...
<!--CodeS-->
procedure TForm1.Button1Click(Sender: TObject);
var
  ERead: DWORD;
  TotalEntries: DWORD;
  UserInfo: lpUSER_INFO_1;
  lpBuffer: Pointer;
  ResumeHandle: DWORD;
  Counter: Integer;
  NetApiStatus: LongWord;
begin
  ResumeHandle := 0;
  repeat
    NetApiStatus := NetUserEnum(nil, 1, 0, lpBuffer, 0, ERead, TotalEntries, ResumeHandle);
    UserInfo := lpBuffer;
    for Counter := 0 to ERead - 1 do
    begin
      listbox1.Items.Add(WideCharToString(UserInfo^.usri1_name) + ' -> ' +
                         WideCharToString(UserInfo^.usri1_comment));
      Inc(UserInfo);
    end;
    NetApiBufferFree(lpBuffer);
  until (NetApiStatus <> ERROR_MORE_DATA);
end;
<!--CodeE-->

UserInfo^.usri1_name -> 요게 사용자 이름입니다~

(김영대님 홈페이지 http://www.howto.pe.kr/ 에 있던거에요 ^^)

그렇군요...
감사합니다. ^^