[Znaper]

Search for this code in the register.php:

if ($verifyemail) {
    $getjoindate=$DB_site->query_first("SELECT joindate FROM user WHERE userid='$userid'");
    $activateid=$getjoindate[joindate];

    eval("\$message = \"".gettemplate("email_activateaccount",1,0)."\";");
    eval("\$subject = \"".gettemplate("emailsubject_activateaccount",1,0)."\";");

    mail ($email,$subject,$message,"From: \"$bbtitle Mailer\" <$webmasteremail>");

  }

After it at this code:

if (!$verifyemail && $welcomeuser) {
    $fromuserid = "1";
    $message = "Insert here your Welcome Message!";
    $title = "Insert here your Subject of the PM!";
    $DB_site->query("INSERT INTO privatemessage (privatemessageid,userid,touserid,fromuserid,title,message,dateline,showsignature,iconid,messageread,folderid) VALUES (NULL,$userid,$userid,$fromuserid,'".addslashes(htmlspecialchars($title))."','".addslashes($message)."',".time().",'0','1',0,0)");
  }