speed up PHP and delete unnecessary please :)

Hello sir madam

Here, I have a configuration problem. I would like an installation type Mercury on my infrastructure. I:

• Mysql 5
  Drupal-6.16
  -Pressflow 6.16
  -PHP 5.2.13
  -Apache 2.2

But I can have properly configured, Apache and PHP together ... . That 's why I come to ask for help please. I often breaks the site where when I have messages like this "INTERNAL ERROR", "NOT FOUND" I'm sure you could help me.

My English is bad, sorry.