SO fiddle
Test Fiddle mainly for SO Questions
by J. Albert Bowden
HTML
<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/overcast/jquery-ui.css">
<fieldset>
<legend>Do you currently have SolidWorks</legend>
<ul>
<li><label for=""><input type="radio" name="solidworks" value="Yes" id="rdYes" /> Yes</label></li>
<li><label for=""><input type="radio" name="solidworks" value="No" id="rdNo" /> No</label></li>
</ul>
</fieldset>
<fieldset id="boxReseller" style="display:none;">
<legend>Who is your SolidWorks reseller?</legend>
<ul>
<li><label for=""><input type="radio" name="reseller" value="Cad Connect" /> Cad Connect</label></li>
<li><label for=""><input type="radio" name="reseller" value="Cadtek" /> Cadtek</label></li>
<li><label for=""><input type="radio" name="reseller" value="CCSL" /> CCSL</label></li>
<li><label for=""><input type="radio" name="reseller" value="Innova" /> Innova</label></li>
<li><label for=""><input type="radio" name="reseller" value="NT CAD/CAM" /> NT CAD/CAM</label></li>
<li><label for=""><input type="radio" name="reseller" value="Solid Engineer" /> Solid Engineer</label></li>
<li><label for=""><input type="radio" name="reseller" value="Solid Solutions Ireland" /> Solid Solutions Ireland</label></li>
<li><label for=""><input type="radio" name="reseller" value="Solid Solutions Management" /> Solid Solutions Management</label></li>
<li><label for=""><input type="radio" name="reseller" value="TMS Scotland" /> TMS Scotland</label></li>
</ul>
</fieldset>
JavaScript
$("input[name='solidworks']").change(function() {
$("#boxReseller").toggle(this.value == "Yes");
});