CREATE PROCEDURAL LANGUAGE plpythonu on windows, with EDB's 8.4.2 installer causes error

When attempting to restore a dump of a database with a pl/pythonu
function, I encountered the following error (recreated here with
psql):

postgres=# \c lustre
psql (8.4.2)
WARNING: Console code page (850) differs from Windows code page (1252)
8-bit characters might not work correctly. See psql reference
page "Notes for Windows users" for details.
You are now connected to database "lustre".
lustre=# CREATE PROCEDURAL LANGUAGE plpythonu;
ERROR: could not load library "C:/Program Files/PostgreSQL/8.4/lib/plpython.dll
": The specified module could not be found.

This is a throwaway VM that I intend to do a little bit of testing on.
I installed python 2.7 for windows, thinking that the module that
wasn't found was another dll that plpython.dll was in turn dependent
on, but doing so hasn't helped - besides, I always understood that the
shipped PLs don't have any external dependencies (the docs indicate
that it's a simple matter of "createlang plpythonu dbname"). It's
quite clear that plpython.dll does exist in the directory specified.
What should I do?

--
Regards,
Peter Geoghegan