Use hidden form fields. For example, instead of this:
Code:
<tr>
<td bgcolor="{secondaltcolor}"><normalfont><b>Use 'Email Notification' by default</b></normalfont><br>
<smallfont>Using this option emails you whenever someone replies to a thread that you have participated in.</smallfont></td>
<td bgcolor="{secondaltcolor}"><normalfont>
<input type="radio" name="[high]emailnotification[/high]" value="yes" checked> yes
<input type="radio" name="[high]emailnotification[/high]" value="no" > no
</normalfont></td>
</tr>
You can use this:
Code:
<input type="hidden" name="[high]emailnotification[/high]" value="yes" />
(where yes can also be no, depends on what you want

)