That's an issue between PHP and IIS, unrelated to OSTicket. Can you get a working phpinfo() page? Is your PHP old/outdated?
I'll assume you are running PHP as an ISAPI module. Can run PHP as a CGI process?
If nothing seems to fix it, stop IIS I'd try this:
http://www.apachefriends.org/en/xampp-windows.html(http://www.apachefriends.org/en/xampp-windows.html)
That will do a full and correct install of everything you need (PHP/Apache/MySQL) to run it on a Windows bax.