You will have to install IIS. If you have XP Pro or at least Vista Home Premium, you just have to go to Add/Remove Programs, Windows Programs and install IIS from there. If you do not have PHP installed, install that now as well.
To view the source... notepad. To view it executed install a web server on your pc.. google 'apache', then install php on your server you just installed google 'php'.
Well I use PHP myself and I run a program called XAMPP. You just install it and then place your php files (and everything else that goes with them) in a folder called htdocs. htdocs is found in the xampp folder that is installed with the program. then all you do is make sure that the program is running, pull up IE and type this: http://localhost/sitename.php