Find:
HTML Code:
<select name="titleonly">
<option value="0" $titleonlyselected[0]>$vbphrase[search_entire_posts]</option>
<option value="1" $titleonlyselected[1]>$vbphrase[search_titles_only]</option>
</select>
Replace With:
HTML Code:
<select name="titleonly">
<option value="0">$vbphrase[search_entire_posts]</option>
<option value="1" selected="selected">$vbphrase[search_titles_only]</option>
</select>