override built-in mail()

Hello Guys/Gals, it's friday (at least where I am it is) and I have an issue with a script that I just started using again. The problem is, is that it uses the built in PHP mail() function, and on my testing server, mail() doesn't work. The other issue, is that I use SMTP Auth to connect to my mail server, so that when mail sends out, it comes from my mail server so that there is less of a chance for being marked as SPAM. So, what I am looking to do, is use either the trust old Pear::Mail or PHPMailer scripts (I am sure there are other ones out there, but those are the 2 I am most familiar with). So now to my actual question. How can I override the built-in PHP mail() function, to let either of those 2 (or something else someone may suggest) to act in the same manner as the mail() function? Is this easy? I've googled, but haven't seen any reference to doing what I am looking to do (maybe I just can't google) Steve