Like many of you who run Windows Vista, I've had trouble getting my machine to recognize my Dingoo when I plug it in the USB port. I found a trick the other day that worked. For whatever reason, my Dingoo likes to be mapped to drive F:. So before plugging in my Dingoo I first plugged in a flash drive. The flash drive was mapped to drive E: so when I plugged in my Dingoo, it went to drive F: and worked just fine.
Of course, your mileage may vary.
Good luck!