junk from my forms output

I have the following in a file called "hello.php" in my htdocs directory
(Apache webroot).

<form action="action.php" method="post">
 <p>Your name: <input type="text" name="name" /></p>
 <p>Your age: <input type="text" name="age" /></p>
 <p><input type="submit" /></p>
</form>

as well as the following in a file "action.php", also in the same directory.


Hi <?php echo htmlspecialchars($_POST['name']); ?>.
You are <?php echo (int)$_POST['age']; ?> years old.

When I click on the submit button of the form in hello.php, it should say
something like:
"Hi Hanson.  You are 33 years old."  But instead of just saying that it also
appends a bunch of junk at the beginning like this:

{\rtf1\ansi\ansicpg1252\deff0\deflang1033{\fonttbl{\f0\fswiss\fcharset0
Arial;}} {\*\generator Msftedit 5.41.21.2509;}\viewkind4\uc1\pard\f0\fs20 Hi
hanson .\par You are 33 years old.\par } �

Can someone help me with this?  Why does my forms reply from action.php
contain so much junk?  I have a Windows installation of PHP and Apache.

thanks,
-Hanson