htaccess query. 2 rewrites rules for 2 home pages - .htaccess

Question

I'm hoping someone might be able to help with a problem I'm having due to my lack of experience and knowledge with htaccess.
What we're doing is running IP Boards forum software and wordpress both in the root directory. The IPB has the index.php file (because of having indexed url's) and the new Wordpress's index.php file has been renamed to blog.php.
At the very top of the htaccess file we've added: DirectoryIndex blog.php index.php - so the new wordpress opens first.
The problem I'm having is trying to have 2 rewriterules in the htaccess file for the friendly urls from the forum software and also the permalinks for the new wordpress.
I can only seem to have one or the other.
Please could anyone tell me, or point me in the right direction to get both working.
This is what I'm doing so far but sadly no joy, but works fine if we remove one of the condition and rewrites.
<IfModule mod_rewrite.c>
Options -MultiViews
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /blog.php [L]
</IfModule>
Many thanks in advance.

Answer 1

Not sure if you still want an answer. Either way, if you are trying to go to two different pages you need some way of distinguishing them.
DirectoryIndex basically tells the default file (and order) when entering a directory. So http://host.com/ with both blog.php and index.php in the directory will serve up blog.php because it is first in the list you gave the server. If there is only index.php, it will serve that. If neither (and you don't have anything else in the list) it will throw a 404 because no default file is found.
EDIT: it will try to list contents if not found. My bad. If you don't allow directory listing, then it will probably show an error code. To turn off directory listing look in options: http://httpd.apache.org/docs/current/mod/core.html#options
http://httpd.apache.org/docs/current/mod/mod_dir.html
Your rewrite rules seem to kind of want do the same thing in a different order. If you request http://host.com/a and a is not a file or directory (according to the conditions) it will go to index.php.. if index.php doesn't exist, then it will loop until the server catches it, because you don't check that. So, that means the second set of conditions don't do anything, because either index.php exists or it doesn't and the next set probably won't really be reached unless it does.
You need to decide how to differentiate the two (/blog/ for the blog.php and / for index.php or something) and make one of them the default. If you want to randomize it, I would suggest doing that through PHP.
http://httpd.apache.org/docs/current/mod/mod_rewrite.html
.. to redirect from root to /forums/ through htaccess try this:
RewriteEngine on
RewriteCond %{REQUEST_URI} !^/forums/
RewriteRule ^(.*)$ /forums/$1 [L]