Hi,
two solutions, the second one is better:
1)
change AddType in httpd.conf from e.g.
AddType application/x-httpd-php .php .html
to
AddType application/x-httpd-php .php .html .inc
and restart apache
2) put all .inc files that are included by php scripts outside the document root and it's subdirectories (might be some work). They'll still work but there would be no way to access them directly (unless there's a security flaw in php that would allow that).