Running two versions of PHP locally

Greetings Gents, I am interested in running two versions of of PHP. I want to see if I can get my boss to buy into migrating to PHP 5. I want to set it up locally. Locally I am running apache on a windows XP box with PHP 4. I would like I would like to be able to set up PHP 5 as well on the server and have some folders/virtual hosts set up in php 4 and others in php 5? Is this possible? How would I go about doing it? Thanks Phillip