Negate the equals sign with a not ("!"):
PHP Code:
<td class="alt2 smallfont"
<if condition="$foruminfo['forumid'] != 0">
{ style="border-bottom:1px solid #4E4E4E;"
}
</if>
><img src="images/misc/controller.png"></td>
The nbsp; code is to keep the style statement from crashing into the class statement. If the style statement isn't sent to the user, then the user's browser will ignore it.
Though, I wonder why you specify a forum number > 1, when there's no such "0 forum" in vBulletin.
Maybe you just want this to display in forums numbered, say, 25 and higher?
PHP Code:
<if condition="in_array($forum['forumid'], array(25,26,27,28))">
Code is off the top of my head, it may need tweaking.