I ran into a problem when trying to install FMS 13.0v1 on a Windows Server 2008 machine. Hope this helps someone else. During the installation the dialog box:
To install FileMaker Server, ports 80 and 443 must be available. The following ports are in use: 80. To disable the websites on these ports, click Disable Websites
would come up. When the button to disable was pressed it would appear to work but when you click the Install button to continue it would repeat. After several hours of testing I discovered that the "Web Deployment Service Agent" was preventing the release of port 80. Stopping (and disabling) this service allowed the FMS 13 installation to continue. I did not re-enable the service after FMS 13 was successfully installed because it is not need on this server so I don't know if it would conflict after installation if it was re-enabled.