Arduino UNO usb not recognized (no reset pin)

Other Hardware 3rd Party Boards
2
  1. You don't have a Uno. You have whatever your cheap knock-off is called.
  2. There is no DFU mode because there is no ATmega8u2 to put into DFU mode
  3. "USB to serial part of the circuit, using PL2303, compared to the original Duemilanove FT232RL, performance is more stable, faster"
    Clearly that isn't the case, because your board isn't working...

Actually the PL2302 is one of the worst USB to Serial chips on the market.

You don't have an official Arduino (or even a decent clone of one). You need to contact whoever you bought the board from for support. This forum won't be of much help.