To expand on TOASTERvan's comment: if you're buying a USB cable, be sure to pay attention to the packaging. Some of them specifically say "charging cable". Sometimes those that are labeled as "charging cable" don't have the two data pins connected at the ends. This makes them more secure to use for charging, if you are plugging in to a USB at the airport, for instance, but means that they are not able to transfer data by design. Double check the packaging, and make sure you know what you are buying.