I have an Arduino Leonardo, bought from RS electronics, and when I plug it in, it shows up as 'ATm32U4DFU' under 'Other devices' in Device Manager. I've tried Update Drivers with the 'C:\arduino\arduino-1.5.5\drivers' IDE folder, and with the 1.0.3 folder, and with the 1.0.1 folder, but nothing... I unzipped 'Old_Arduino_Drivers' and it doesn't find it in there either.
I ran 'dpinst-amd64.exe', those drivers installed successfully, but it doesn't show anything different under Device Manager.
In the IDE, the 'Ports' is greyed out, and it can't find the Leonardo in any of my USB ports.
I have 3 USB 2.0 ports and 1 USB 3.0 port. It doesn't matter which one I plug it into. Still comes up as ATm32U4DFU and won't install drivers from the /drivers directory
That looked good... but i think my Leonardo is broken now
I did all the instructions until the very last one, click 'Start Application' and then it says:
com.atmel.flip.IspException
Could not write to USB device.
So now it shows up in Device Manager under 'Atmel USB Devices' as ATmega32U4.
But the Arduino IDE still has "Serial Port" greyed out, and says "Couldn't find a Leonardo on the selected port. " etc.
I'm new to all of this, so take this comment with a grain of salt.
I've been fighting with my uno for over a week now with this same issue. What seems to be working for me now is to unplug the usb from the computer. Then in device manager right click on Ports (Com & LPT). That brings up a menu that says "scan for hardware changes" or "properties" Then, before I select Scan for hardware changes, I hold down the reset button of the Uno and plug it back in. Then I hit scan and let the reset button go. So far it's worked twice. Far from a proven method, but after hours and hours of trying everything ever suggested for every arduino thats ever existed, this is the only thing that's worked for me even once. It still doesn't clear my "Serial port COM3 already in use error, but I have a mallet here that I think might do the trick.