Debugging PHP issues on Windows can be tricky. I'd enable logging so you can see what the actual errors are. These lines in php.ini:
log_errors = On
error_reporting = E_ALL
error_log = C:\Windows\System32\LogFiles\php-errors.log
or something like that just so you can see the actual errors PHP is getting. And in config.php:
$CFG->dbtype = 'mariadb'; // 'pgsql', 'mariadb', 'mysqli', 'mssql', 'sqlsrv' or 'oci'
$CFG->dblibrary = 'native'; // 'native' only at the moment