Microsoft's Halo 2 Video Game Leaked on Internet  SEATTLE (Reuters) - Halo 2, the sequel to Microsoft Corp.'s  &lt;A HREF="http://www.reuters.co.uk/financeQuoteLookup.jhtml?ticker=MSFT.O qtype=sym infotype=info qcat=news"&gt;MSFT.O&lt;/A&gt; best-selling game for its Xbox video console, has  leaked onto the Internet nearly four weeks before its planned  sale, the world's largest software maker said on Friday.