Perl is a required component for this method of allowing the submission of FirstClass forms by unauthenticated users. Perl comes installed under OS X, but if you are running a Windows Internet Services, you must download and install Perl before you can proceed. You must download and install Active Perl on the same computer that you are running Internet Services.
You can download the most recent version of Active Perl for Windows from the Active State web site (http://www.activestate.com/activeperl/downloads).
Run the installer, accepting all default options.
At the root level of that drive you will find a folder called Perl64.