Yes, just have your direct address (sitename.com/index.htm) as some html page, which would re-direct you to the forum after few seconds.
CODE
<HTML>
<HEAD><TITLE>BLANK</TITLE>
<meta http-equiv="refresh" content="10;URL=http://www.sitename.com/forums/index.php">
<HEAD>
<BODY>Deliberately left blank. <BR>
You need to personally contact this person, to know any more details, about which directory/file you want.
<br>Anyway, You will be redirected to a forum in 10 seconds.
<br><img src="wait.gif" alt="please wait 10 seconds for re-direction"><!-- bt --></body>
</html>
The above is an example.
Hoping this helps....