First of all, I suppose this is for testing purposes, if not, installing and securing a web hosting in your home or office is not a good idea, unless you really know what you are doing.
So, install PHP following the installation instructions
Then open the shell (cmd.exe) and run :
Configuration File (php.ini) Path: C:\Windows
Loaded Configuration File: C:\Program Files (x86)\Zend\ZendServer\etc\php.ini
Scan for additional .ini files in: (none)
Additional .ini files parsed: (none)
So, in my installation the configuration file is C:\Program Files (x86)\Zend\ZendServer\etc\php.ini
In the configuration file, add or modify this fields:
SMTP = mail.mydomain.com
smtp_port = 25
Then every time you call the function mail() from a php script, will try to send the email using this configuration.
IF YOU DONT HAVE A SMTP SERVER, you will need one. IIS does not provide an SMTP server as far as I know, it use to, but if I'm not mistaken, you need MS Exchange now...