Go to your AdminCp -> Styles & Templates -> Edit Templates (in your style) -> Search for template called
newreply.
Search this code:
Code:
<form action="newreply.php?do=postreply&t=$threadid" name="vbform" method="post"<if condition="!is_browser('webtv')"> onsubmit="return vB_Editor['$editorid'].prepare_submit(0, $vboptions[postminchars])"</if>>
<table class="tborder" cellpadding="$stylevar[cellpadding]" cellspacing="$stylevar[cellspacing]" border="0" width="100%" align="center">
<tr>
And change the width.
Do the same for the
newthread template.