Nintendo Prepares Weekend Launch of New Handheld  LOS ANGELES (Reuters) - A generation of children grew up  playing Nintendo Co. Ltd.'s &lt;A HREF="http://www.reuters.co.uk/financeQuoteLookup.jhtml?ticker=7974.OS qtype=sym infotype=info qcat=news"&gt;7974.OS&lt;/A&gt; Game Boy handheld video  game system, and now that they've grown up, Nintendo has a new  toy for them.