You can extract a new copy of rundll32.exe and rundll.exe from the Win Me cab
set.

Both Rundll.exe and Rundll32.exe are contained in WIN_17.CAB of the Win Me cab
set and can be restored using MSConfig | General | Extract File ... and
following the prompts.  The "cab" files are in the Win9x folder on the Win Me
CD and/or in a sub-folder of Windows\Options.  See MS  KB129605 - "HOW TO:
Extract Original Compressed Windows Files"
(http://support.microsoft.com?kbid=129605).

Alternatively use system restore to roll your system back to before you
deleted rundll32.exe and rundll.exe provided that that was not more than a few
days ago.