Gateway's Quarterly Loss Narrows  SAN FRANCISCO (Reuters) - Personal computer maker Gateway  Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=GTW.N target=/stocks/quickinfo/fullquote"&gt;GTW.N&lt;/A&gt; on Thursday posted a net loss that narrowed from a  year earlier and bettered its own forecast, helped by higher PC  sales and lower costs.