Here's a good article about setting up two different PHP version on the same machine at the same time.
Rather than have to append ":8080" to each URL you want to use, can you set up two different user accounts (windows xp pro) each with a different version of php with all else being equal?
For example, I would add a user called, "PHP5 - MySQL5" which would have PHP version 5 and MySQL 5. Then set up another user account for PHP 4.3 and MySQL 4.1.
I've figured out, with longneck's help, how to run two different verisons of MySQL at the same time but this new idea would help keep everything separate.
Any thoughts or idea expansion is appreaciated!