vbulletin forum is getting redirected to activty.php

Once you will upgrade your vbulletin forum to latest version 4.2 you will find that by difault forum is being redirected to activity.php which is not desired in most of the cases. Mostly forum.php should be displayed as default page of forum. Although prior to vbulletin 4.2 we are suppose to make changes in index.php(…)