Apple (Nasdaq: AAPL) is now the top music retailer in the United States -- ahead of Wal-Mart (NYSE: WMT), Best Buy (NYSE: BBY), Amazon (Nasdaq: AMZN), and Target (NYSE: TGT). So will the music last for Apple's iTunes, or will Microsoft's (Nasdaq: MSFT) Zune finally find its rhythm? It's been a rough year for the Chinese stock market; is American Oriental Bioengineering (Nasdaq: AOB) the right medicine for investors? And which other emerging-market stocks have big potential?  Chris Hill looks at some of the stories on the Fool radar and shares a secret about your mortgage.

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