For win32 base free SMTP server, try www.postcastserver.com (this may not work in case, your computer is standalone type, DNS is required for PostCast to function properly).
The other way, is to set SMTP and send_form entries under 'mail function' directive in your php.ini to your ISP's SMTP server and email address for that particular ISP accordingly.
It still may not work because some ISP required checking authenticate (in some form) prior to forwarding your message to reduce spaming possibility.
