UNO not recognized ATmega328 OK board not OK

Hi, problems with Arduino UNO not being recognized by Windows

  • I have two Arduino UNO's
  • One works OK, the other one is invisible to winows VISTA.
  • Same PC, same cable, same all.
  • Switched ATmega from boards and ATMEGAs are OK, but problem is with one board
  • Originally both work OK.
  • Invisible UNO was working, but suddenly stopped being recognized while running
    shifting leds sketch and opening serial monitor
  • when shifted ATmegas, the one on good board took blinking led sketch an ran OK on
    bad board, OK board continue to be OK with the other AT mega.
  • Did the boothloader transfer using UNO as ISP, Rx, Tx and Rx2 LEDs blinked for few
    minutes Good transfer message appeared, but still windows will not see.

Any ideas on how to fix????

I hope I did not confuse for any posible problem solver, when I write that I switched the ATMEGAS I meat to say
I swicthed the IC chips from what I have as bad board and installed on good board, then I installed the IC chip from good board on bad board and the IC chips (big ones with 28 pins each) and error will follow the board.
I tried to write the firmware into the bad board using flip, but when I ask flip to open the USB communications it says it is unable to do so, also when i try to open the HEX file it says address is out of range