I am using xampp latest version (just downloaded), installed it normally with no issues.
I downloaded the latest version of phpbb3, renamed the folder to 'support' without the quotes of course then copied the folder to /htdocs/support
I created the db in phpMyAdmin and then visited http://127.0.0.1/support/ where I get the following...
Forbidden
You don't have permission to access this resource.
Apache/2.4.58 (Win64) OpenSSL/3.1.3 PHP/8.0.30 Server at 127.0.0.1 Port 80
It is fine if I go to http://127.0.0.1/index.php where I created an empty index.php file. I am running Windows 11 64bit and no ports are blocked. I only get the Forbidden when trying to access any file or folder beyond /support/