You will have to do this for all the delete templates I think, would just be easier to tell the mods to hard delete it! Anyway
Goto to the AdminCP -> Styles and Templates -> Style Manager -> (From the Right) Edit Templates -> (From the large select box) Thread Administration Templates -> threadadmin_deletethread
Find the thing in Red and move it to the place I've shown in Green. You'll probably need to do something similar for threadadmin_deleteposts, threadadmin_deletethreads.
<if condition="$show['softdelete']"><div>
<label for="rb_deletetype_1"><input type="radio" name="deletetype" value="1" id="rb_deletetype_1" checked="checked" />$vbphrase[soft_delete_leave_deleted_message]</label>
<br /><img class="inlineimg" src="$stylevar[imgdir_misc]/tree_$stylevar[textdirection].gif" alt="" border="0" /><label for="cb_keepattachments"><input type="checkbox" name="keepattachments" class="inlineimg" value="1" id="cb_keepattachments" />$vbphrase[keep_attachments]</label>
</div></if>
<if condition="$show['harddelete']"><div>
<label for="rb_deletetype_2"><input type="radio" name="deletetype" value="2" id="rb_deletetype_2" checked="checked" onselect="alert('moo')" />$vbphrase[physically_remove]</label>
</div></if>
</td>
</tr>
<tr>
<td>
$vbphrase[reason_for_deletion]:<br />
<input type="text" class="bginput" name="deletereason" value="$threadinfo[del_reason]" size="50" maxlength="125" />
</td>
</tr>
</table>
</fieldset>
</div>
</div>
<div style="margin-top:$stylevar[cellpadding]px">
<input type="submit" class="button" value="$vbphrase[delete_thread]" accesskey="s" />
<input type="reset" class="button" value="$vbphrase[reset_fields]" accesskey="r" />
</div>
</td>
</tr>
</table>
</form>