If you try to transfer a large amount of data to a usb device and the device keeps spontaneously disconnecting or if your iPod/iPhone errors out while syncing (Attempting to copy to the disk “YOURDEVICENAME” failed. The disk could not be read from or written to.”), there are two probable solutions:

 
  1. In Device Manager, open the properties for the USB Root Hub. Uncheck “Allow the computer to turn off this device to save power” on the Power Management tab.
  2. Switch the device to a USB 2.0 port. Older USB ports are too slow to handle the transfer rates required for gigabytes of data. If your computer is like mine and doesn’t have any 2.0 ports, you can install a PCI to USB card. They’re cheap (<$10) and well worth it for the extra speed and reliability.