Where can I change XAMPP configuration?
 

You adjust XAMPP with (classic text) configuration files. The following files exist:
Apache basic configuration: .\xampp\apache\conf\httpd.conf
Apache SSL: .\xampp\apache\conf\ssl.conf
Apache Perl (only addon): .\xampp\apache\conf\perl.conf
Apache Tomcat (only addon): .\xampp\apache\conf\java.conf
Apache Python (only addon): .\xampp\apache\conf\python.conf
PHP: .\xampp\apache\conf\php.ini
(with the apache actual running php version)
MySQL: .\xampp\mysql\bin\my.cnf
phpMyAdmin: .\xampp\phpMyAdmin\config.inc.php
FileZilla FTP: .\xampp\FileZillaFTP\FileZilla Server.xml
Mercury Mail basic configuration: .\xampp\MercuryMail\MERCURY.INI
Sendmail: .\xampp\sendmail\sendmail.ini