I'm guessing that your mapping still isn't set up completely. On your configuration page the path to your perl executable should look like this:

c:\perl\bin\perl.exe -T %s %s
[download]

This is similar to an answer given here that illustrates setting it up through the registry, but you can also do it through the application configuration like you did.

The -T turns on taint checking which you should always use for a public server.

ryddler