下面的代码是中国微软的代码，你可以参考着写。

<script LANGUAGE="JavaScript">
<!--
function load(form) {
var url = form.list.options[form.list.selectedIndex].value;
if (url != "") open(url, "_self");
return false;
}

// -->
</script>

<form NAME="menu" onSubmit="return load(this)">
<p><select id="select2" name="list" onChange="load(this.form)" size="1" class="90V" style="background-color: rgb(196,226,103)">

<option selected > ** 免费下载 **</option>
<option value="/china/msdownload/">软件下载首页</option>
<option value="/china/msdownload/nt.htm">Windows NT </option>
<option value="/china/msdownload/office.htm">Office</option>
<option value="/china/msdownload/dwnie5.htm">Internet Explorer</option>
<option value="/china/msdownload/wince.htm">Windows CE SDK</option>
<option value="/china/msdownload/pinyin.htm">微软拼音输入法</option>
<option value="/china/msdownload/y2k.htm">Year2000 相关程序</option>
<option value="/china/msdownload/backoffice.htm">BackOffice</option>
<option value="/china/msdownload/seminar.htm">微软活动讲座资料 </option>
</select></p>
</form>