DB Table names re-write in 2.0, 2.6 upgrade problem

In my copy of WordPress 2.0, I rewrite the Table names of the wp-settings.php file as follows:

// Table names
$wpdb->posts = $table_prefix . ‘ayush_posts’;
$wpdb->users = $table_prefix . ‘ayush_users’;
$wpdb->categories = $table_prefix . ‘ayush_wpcategories’;
$wpdb->post2cat = $table_prefix . ‘ayush_wppost2cat’;
$wpdb->comments = $table_prefix . ‘ayush_wpcomments’;
$wpdb->links = $table_prefix . ‘ayush_wplinks’;
$wpdb->linkcategories = $table_prefix . ‘ayush_wplinkcategories’;
$wpdb->options = $table_prefix . ‘ayush_wpoptions’;
$wpdb->postmeta = $table_prefix . ‘ayush_wppostmeta’;
$wpdb->usermeta = $table_prefix . ‘ayush_wpusermeta’;

Now, I downloaded and trying to upgrade to version 2.6, even after I set up all the values of wp-config.php file, I cannot upgrade it.

My website URL is ayush.khampat.com, when I open it will take me to wp-admin/install.php. I enter ayush.khampat.com/wp-admin/upgrade.php, instead of opening the file, it will try to download the whole file. So, how to fix this thing? Please, help me.