Walgreen Boosts Profit, Plans More Stores  NEW YORK (Reuters) - Walgreen Co. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=WAG.N target=/stocks/quickinfo/fullquote"&gt;WAG.N&lt;/A&gt;, the top U.S.  drugstore chain, on Monday said quarterly profit rose 18.1  percent due to rising prescription demand and strong sales from  its highly profitable nonpharmacy segment, including digital  photo processing.