I'm trying to add some PHP includes to my sites home non-vB page. I'm not too familiar witht his stuff but I follow directions well

Anyway, I'm using <? include("vbforums/filename.php"); ?> to read the info but I keep getting the following error:
Fatal error: Failed opening required './admin/config.php' (include_path='.:/usr/local/lib/php') in /home/www/mysite/vbforums/global.php on line 96
I've received this error on several different hacks I've attempted. What can i do to remedy this?