I found a solution to my problem if anyone is interested. I set HTTrack to
download the following sites.

<http://forum.trek-rpg.net/forumdisplay.php?s=&f=24&page=1&pp=25&sort=lastpost&order=desc&daysprune=-1>
<http://forum.trek-rpg.net/forumdisplay.php?s=&f=24&page=2&pp=25&sort=lastpost&order=desc&daysprune=-1>
..
<http://forum.trek-rpg.net/forumdisplay.php?s=&f=24&page=14&pp=25&sort=lastpost&order=desc&daysprune=-1>

Next I used these scanning rules.

-*
+*.jpg +*.gif +*.png +*.css +*.js +*.pdf
+forum.trek-rpg.net/showthread.php?t=* 
+forum.trek-rpg.net/forumdisplay.php?s=&f=24*

Lastly I set the Maximum Mirroring Depth (under Limits) to 2, and Maximum
External Depth to 0.

Hope this helps someone else.