Well I can't remember how I resolved my Path_Info issues with iis a couple years ago because it was several tries till it worked. But I remember I did edit php.ini and added
Quote
Set cgi.fix_pathinfo=1
cgi.fix_pathinfo provides *real* PATH_INFO/PATH_TRANSLATED support for CGI. PHP's previous behavior was to set PATH_TRANSLATED to SCRIPT_FILENAME, and to not care what PATH_INFO is. For more information on PATH_INFO, see the cgi specifications. Setting this to 1 causes PHP CGI to fix its paths to conform to the specification.
This came from microsoft web site HERE this applies to fast cgi and IIS6.

Also I found that I had a variable called "ORIG_PATH_INFO" that did work and I might of hacked that in the ubb file "ubbthreads.inc.php".
There is a more current post at this site HERE by Rick. That states that it was omitted in error at one time in the script to look for it as a secondary variable.

Thats all I remember doing but...

It finally worked but I have since moved From IIS to Apache

Blue Man Group
There is no such thing as stupid questions. Just stupid answers