pg_dump on 64-bit windows 2003 server

Hi,

I am trying to run pg_dump on windows 2003 server. I want to run this as a
batch process, so I have specified my password in the
%appdata%\postgresql\pgpass.conf file, however, when this is specified, I
get the following DOS error:

"The image file D:\PostgreSQL\8.3\bin\pg_dump.exe is valid, but is for a
machine type other than the current machine."

Along with a Windows dialog box:

"The program or feature '\??\D:\PostgreSQL\8.3\bin\pg_dump.exe" cannot start
or run due to incompatibility with 64-bit versions of Windows. Please
contact the software vendor to ask if a 64-bit Windows compatible version is
available."

When I run with the command line args:

pg_dump.exe --file="\\soba\backup2\trac_cygna_main\full\backup"
--username=trac_cygna_main_user trac_cygna_main

(or even with no command line args for that matter)

I have tried setting the pgpassfile environment variable (in case spaces in
the current appdata path were causing issues) and still I get the same
message. Should I be doing something different?...or is pg_dump not
supported on 64-bit windows?

Thanks in advance,

-James