Sony Takes on iPod with New Hard Disk Walkman  AMSTERDAM (Reuters) - Sony Corp &lt;A HREF="http://www.reuters.co.uk/financeQuoteLookup.jhtml?ticker=6758.T qtype=sym infotype=info qcat=news"&gt;6758.T&lt;/A&gt; unveiled its first  MP3-compatible, hard disk Walkman music player on Tuesday in an  attempt to recover ground lost to Apple Computer's &lt;A HREF="http://www.reuters.co.uk/financeQuoteLookup.jhtml?ticker=AAPL.O qtype=sym infotype=info qcat=news"&gt;AAPL.O&lt;/A&gt;  iPod.