Rich,
there are basicly two things you could do:
1.) You redirect to an other URL (that means th the user will see a different URL in his webbrowser):
Do something like this:
<?php
// Do your php-stuff here
header("Location: url/of/your/htmlfile.html");
?>
NOTE: It is important that NOTHING is printed out before the "Location..."-part.
This means that the leading <?php... has to be in the first line and first col. of your php-file. (You'll get a warning like "Couldn't write additional header" otherwise).
2.) You include the HTML-file (URL won't change in user's webbrowser)
Do this:
<?php
// Do your php-stuff here
include ("path/of/your/htmlfile.html");
?>
Keep in mind that relative links in your html-file might die because if php-file ande html-file are in different directories.
Cheers, Markus