PHP

There is a good chance you know this already but the default memory setting for PHP on the server is too small to run a Drupal site that has multiple modules.

When I started the process of upgrading my site, I assumed I might have an issue with MySQL and PHP versions. In fact, it was this concern that slowed my initial start. After reading the varies INSTALL.txt files, I saw that upgrades shouldn't be an issue. So, I upgraded and as it turns out, both sites run ok on PHP 4.4.0 and MySQL distribution 3.25.

Knowing, however, that there were modules in D6 that needed PHP5.2, I ventured forward and upgraded both MySQL and PHP to their latest stable versions.