Arduino was working fine in Win 7 and now it doesn´t: I can´t upload code to it

Hi there!
I´ve been using the arduino Mega 2560 for some weeks now, mostly during my holidays. I wanted to learn to program with it. I´ve been using a notebook with Windows 7 (32) and bluetooth capability.
It worked just fine.

Now, at my home, I wanted to install it in my desk PC. My desk PC runs Windows 7 (64) and has bluetooth capabilities.

Now, after installing it, I´ve have some problems to set the COM4 port (it was greyed out at first), but now the PC recognizes the Arduino.
I´ve added the bluetooth antenna to start testing again, and I can´t get the code to be uploaded to the Arduino.

This is the error:

Binary sketch size: 5.308 bytes (of a 258.048 byte maximum) - 2% used
avrdude: ser_open(): can't open device "\\.\COM4": Access is denied.
avrdude: ser_drain(): read error: The handle is invalid. Problema subiendo a la placa. Visita para sugerencias.

I´ve read all suggestions, and everything seems fine: The COM port is there, it seems to work ok.
The weird thing is that at first, when it was greyed out, all COM ports appeared "occupied" up until the 256, which wasn´t being recognized by the arduino. So I´ve changed it to COM4, and it worked: The COM port selection wasn´t greyed out, and I´ve selected the COM4. I´ve then uploaded the blink example, and it worked.

After adding the antenna, everything went wrong, because the error appeared. I´ve tried resetting the arduino, and it worked only once.
I´ve tryed uploading with the antenna connnected and disconnected.
I´ve read that there are some issues with win64, so i´ve followed all instructions available about how to install arduino there.

I´ve read within the error that "COM4": Access is denied." How may I "open" it, when it´s already open and it worked?

Any ideas on what could be wrong? I can´t disable bluetooth in this PC, because the mouse uses it!

Thanks for your insight!!!


Did you install the Arduino 'driver' on the desk machine?

"An ATmega16U2 (ATmega 8U2 on the revision 1 and revision 2 boards) on the board channels one of these over USB and provides a virtual com port to software on the computer (Windows machines will need a .inf file, but OSX and Linux machines will recognize the board as a COM port automatically. "

"4 | Install the drivers

Installing drivers for the Arduino Uno or Arduino Mega 2560 with Windows7, Vista, or XP:

Plug in your board and wait for Windows to begin it's driver installation process. After a few moments, the process will fail, despite its best efforts

Click on the Start Menu, and open up the Control Panel.

While in the Control Panel, navigate to System and Security. Next, click on System. Once the System window is up, open the Device Manager.

Look under Ports (COM & LPT). You should see an open port named "Arduino UNO (COMxx)"

Right click on the "Arduino UNO (COmxx)" port and choose the "Update Driver Software" option.

Next, choose the "Browse my computer for Driver software" option.

Finally, navigate to and select the driver file named "arduino.inf", located in the "Drivers" folder of the Arduino Software download (not the "FTDI USB Drivers" sub-directory). If you are using an old version of the IDE (1.0.3 or older), choose the Uno's driver file named "Arduino UNO.inf"

Windows will finish up the driver installation from there.

I have the same problem. Arduino Nano and Windows 7 64b.

The solution is not good for me... =(

Any other idea, please?



When installing driver, just pointing to the driver folder gives an error:

"Windows was unable to install your ATmega16u2 DFU

“Windows could not find software for your device.”

Forcing it by Have Disk and pointing to arduino.inf works but:
"Windows found driver … …but encountered an error while installing it
Arduino Uno

This device cannot start (Code 10)