Can't Upload to Uno


I allowed Microsoft to install some updates yesterday and today I can't upload. I get the error message

"Arduino: 1.6.4 (Windows 7), Board: "Arduino Uno"

Sketch uses 450 bytes (1%) of program storage space. Maximum is 32,256 bytes.

Global variables use 9 bytes (0%) of dynamic memory, leaving 2,039 bytes for local variables. Maximum is 2,048 bytes.

avrdude: ser_open(): can't open device "\.\COM4": The system cannot find the file specified.

Problem uploading to board. See for suggestions.

This report would have more information with
"Show verbose output during compilation"
enabled in File > Preferences."

I am running Windows 7 and have a Uno board connected with a USB cable.

When I open the Arduino software it says I have a Uno on COM 4. If I open the Tools tab, the port option is grayed out. If I open the preferences.txt file it says that the serial port is COM3.

If I open the Device manager I can't find the COM ports anywhere.

In frustration, I uninstalled the older Arduino Software and installed ver 1.6.4. That didn't help and have the same problem.

How do I fix this? Is it happening to others as well?

Lastly, with the previous software one of my sketches was automatically loaded when I opened the Arduino software. How do I do this with 1.6.4?

Thanks for your help!

Try quitting the arduino application and reopening it


I did that several times. No fix. I believe a new set of Windows upgrades has stopped allowing the use of unsigned drivers. It removed them and won't let you reinstall them.

I have tried uninstalling, reinstalling, turned off driver check and can't get the virtual drivers to load. More people will be having this problem very soon.

Hopefully someone can tell us how to fix it.