I have a non-standard installation of WAMP. I've installed it to my Z:/wamp. Recently it stopped working. All the suggestions I found on the web told me to check port 80, or check the apache_error.log but that didn't help. I've already moved apache to port 81, and nothing was written to the log.
The solution was to open up a command prompt (cmd.exe), cd into the apache bin directory (Z:\wamp\bin\apache\apache2.2.22\bin for me), and run httpd.exe manually. As soon as I did that, it told me:
Syntax error on line 22 of Z:/wamp/bin/apache/apache2.2.22/conf/extra/httpd-auto index.conf:
<Directory "c:/Apache2/icons">path is invalid.
Which was an easy enough fix; just point it to Z:/wamp\bin/apache/apache2.2.22/icons. Bam! Works again. Just close out of the console and restart WAMP via the icon.
tl;dr If your apache won't start, and the error log isn't giving you any information, start it manually and check there if you get any error messages.
Edit: I know this blog post is formatted stupidly, I have to figure out what's going on with WordPress. [Fixed Sept 13, 2026]