Find the template and put a condition around the stuff:
HTML Code:
<if condition="$forumid != 'x'">
stuff to show if not forum x
</if>
To find the template to modify, do this - vboptions > General Settings > Add Template Name in HTML Comments > set to Yes . Then go back to your page and view the source code and you will see the name of the template called around your part of the code. Sometimes the template is the one mentioned at the very top of the page source.
If you have further problems, post the exact code in the templates you are using, along with the template name.