Microsoft Launches New Media Center PC  SEATTLE (Reuters) - Microsoft Corp. &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; on Tuesday  unveiled a new version of its Windows XP Media Center, adding  features such as instant messaging and high-definition  television to a personal computer designed for the living room.