If you integrate PHP via FastCGI on the IIS 7.5, each script is aborted after 600 seconds (i.e. 10 minutes) by default. A change of the known variable "max_execution_time" in the php.ini has no influence on this, you (also) have to adjust the FastCGI settings. For this, the IIS offers a comfortable interface for managing the relevant variables.
To do this, open the Internet Information Services (IIS) Manager, click on the appropriate server and then on FastCGI Settings:
After double-clicking on php-cgi.exe you will find the relevant options "Activity timeout" and "Request timeout" under "Process model":
These two values can now be increased to 7200 each to extend the timeout to 2 hours.