Installing and upgrading help

hi,

I have successfully upgraded from 1.6.4 to 1.7.1 when i try to login, i get this error on the page

Fatal error: Call to undefined function: forum_tp_can_track_forums() in /home/drrogu/public_html/adoptionnclasses/classroom/course/lib.php on line 1098

I can see some menus on the left which point to different courses but i do not see the whole screeen to i can access the admin panel and disable the forum

how do i disable the forum now. if it is the forum which is not working.