Archives page not generated out of index.php?

Actually you might be able to do it. In wp_options table there is “blogfilename” which is set to index.php. I suppose you could change it to something else.

wp-admin/options.php

You could also change the DirectoryIndex to something other than index.php. On many servers index.html is served up before index.php. For instance my htaccess file is set to:
DirectoryIndex index.html index.html.var index.php index.shtml

If there is an index.php and index.html file in the same directory, index.html is displayed.

It needs to go into the main WP folder or else it won’t work. Perhaps you need to change the permission levels on the file itself. Did you try to change the blogfilenam to something else as an alternative?

The “line in the code” is actually an option not normally displayed in the admin section. Enter what I gave above, “wp-admin/options.php”, and change the value for “blogfilename” – you will then have to enter that filename to get the blog.

Fortunately it easy to change back as it sounds like you want to do something you don’t fully understand.

Unless you are running a different version of WP, then there is and it does ;-).
http://yoursite/wp-admin/options.php

Under “All Options” it is the sixth option down.
active_plugins
admin_email
advanced_edit
blacklist_keys
blogdescription
blogfilename

Learn something new every day. Must be a holdover from an older version that is no longer used but is still called in template-functions-category (probably an oversight).

Looks like we are stuck unless someone else has an idea or two.