[Xenon]

open editpost.php and find this lines:

PHP Code:

if ($getfirst[postid]==$postid) {
      // delete thread
      if ($getperms[candeletethread]) {
        deletethread($threadinfo[threadid],$foruminfo[countposts]);
        updateforumcount($threadinfo[forumid]);
        eval("standardredirect(\"".gettemplate("redirect_deletethread")."\",\"forumdisplay.php?s=$session[sessionhash]&forumid=$threadinfo[forumid]\");");
      } else {
        show_nopermission();
      }
    } 


just change

PHP Code:

if ($getfirst[postid]==$postid) { 


to

PHP Code:

if (($getfirst[postid]==$postid  && bbuserinfo[usergroupid]!=2) { 


when only normal users cannot delete the thread

or just kill the whole true clause when nobody should delete a thread on this way