Hmm from what I can see you'll need to edit the template:
forumdisplay
Find the code similar to this
Code:
<!-- icon key -->
<table cellpadding="2" cellspacing="0" border="0" width="{contenttablewidth}" {tableinvisibleextra} align="center">
<tr><td colspan="5" align="center"><smallfont>$timezone</smallfont></td></tr>
<tr><td rowspan="2" width="50%"> </td>
<td nowrap><smallfont><img src="{imagesfolder}/newfolder.gif" border="0" alt="New Posts"> <b>New posts</b> </smallfont></td>
<td nowrap><smallfont>( <img src="{imagesfolder}/newhotfolder.gif" border=0 alt="Hot Thread"> <b>More than $hotnumberposts replies or $hotnumberviews views</b> ) </smallfont></td>
<td nowrap><smallfont><img src="{imagesfolder}/lockfolder.gif" border="0" alt="Closed Thread"> <b>Closed thread</b></smallfont></td>
</tr>
<tr>
<td nowrap><smallfont><img src="{imagesfolder}/folder.gif" border="0" alt="No New Posts"> <b>No new posts</b> </smallfont></td>
<td nowrap colspan="2"><smallfont>( <img src="{imagesfolder}/hotfolder.gif" border=0 alt="Hot Thread"> <b>More than $hotnumberposts replies or $hotnumberviews views</b> ) </smallfont></td>
<td rowspan="2" width="50%"> </td></tr>
</table>
<!-- /icon key -->
and delete that. I think that will cover everything