apache won't start

Hi my windows won't start apche for some reason. I have windows xp service pack 2. I previously installed IIS on my machine. I changed the port for IIS to 8080 and checked to make sure that port 80 isn't taken. I previosly installed php 5 a few days ago. It was working fine when I installed mysql and Iis, and PHP a few fews ago, but when I tried to install Apache today, it won't start. It started when I first installed and then it stopped woring all together. I enable my firewall to not block the port. The error message says "window could not start Apache 2.2 on local server. specific error on code 1. I am following the book "dreamweaver cs3 with css ajax and php. so what am I doing wrong?