[Windows 2003 Server/ Windows XP] External Authentication Problem

I'm running ejabberd on a Windows 2003 Server and a Windows XP machine but i can't get 'External Authentication' to work.

I use the following lines in my config file:

{auth_method, external}.
{extauth_program, "C:\\Program Files\\ejabberd-2.0.0\\conf\\test.py"}.

I also tried Perl, PHP and C# scripts but i always get the following error:

=ERROR REPORT==== 2008-04-10 09:29:29 ===
Error in process <0.287.0> on node 'ejabberd@xxxxx' with exit value: {einval,[{erlang,open_port,[{spawn,"C:\Program Files\ejabberd-2.0.0\conf\test.py"},[{packet,2}]]},{extauth,init,2}]}

Does anyone know how i can solve this problem?
Thanks in advance.