I have some experience with a few Arduino projects.
Recently (June 2015 http://www.robot-italy.com/it/arduino-uno-r3.html ) I bought another original Uno R3 (backside stamped “Arduino.org”). My IDE (v1.0.6.) runs under Windows 8.1 and I could program my new UNO without any problems. On this application, is a solar dryer control, I am measuring temperature and humidity and doing control of the built in warm air fans. With the USB serial interface, I am writing logged data to a connected PC (with a terminal emulator). As I said before, everything works fine with my windows 8.1 PC.
For doing some data capturing over a few days I had the idea to use my old Windows XP SP3 PC, but I was not able to install the USB driver, for having a communication channel to the UNO. On this PC I have also IDE 1.0.6 and older Arduino UNO R3 (backside stamped “arduino.cc”) are working fine with no problems.
Can anybody give me a hint, how to install the USB driver under Windows XP for the new UNO R3 (Arduino.org)? I already tryed out diffrent hints for driver installations but with no success.
I'm guessing it could be the arduino.org firmware on the ATmega16U2 has a different USB VID/PID so it would be logical to get the drivers for XP from that site.
If you have been keeping up with the news about the feud between arduino.cc and arduino.org you heard arduino.org has done some things such as release a higher numbered Arduino IDE which has some differences from the arduino.cc IDE at version 1.6.5, and I'm sure they are probably including the drivers for the more recently produced arduino.org boards in the higher numbered release. And they have their own forum on that web site as well, although last time I checked the participation was less.
To ensure I could continue to use one IDE, and to use the arduino.cc release and continue participation over here, I would probably load the stock arduino.cc firmware onto the ATmega16U2 so that way it would be like the other Arduinos I already have.
Yes. Each company claims to be the official site. It is more than UNO, it is the Arduino brand itself. If you will continue to use the arduino.org IDE then you may want to go to their forum over there for questions that come up regarding the use of it. Or you may be able to go back to using 1.0.6 or 1.6.5 from arduino.cc since you now have the driver situation fixed, and perhaps stay over here on this forum. I guess we all have to pick what side of the fence to live on.