that leads me to my next point! the way you're doing this is kind of weird. I would suggest setting up one main file that handles all of your requests, and then having other pages that are included that contain all of your content.
this recent thread has plenty of examples posted by myself on good ways of implementing this. this would make maintenance on your part much easier, too. if you like the look of filenames in your URLs rather than query strings (eg. about.php vs index.php?page=about), you can look into Apache's mod_rewrite to mask your URLs (so that /about/ or /about.php redirects to index.php?page=about) -- or if you're using IIS, I've heard it has some URL rewriting module now.
sorry for the long-winded post!
oh, and if you have any questions about implementing a system where one main file handles all of your requests, I'd suggest posting it in this thread rather than that other one! I'd be happy to help.