Cannot save files on usb drives

Hi guys, I’m using the virtual desktop with comodo firewall and I’m trying to save a file from firefox on a usb drive but even though I have included the folder in the “do not virtualize” list, I receive the message that the folder is write protected and I cannot save the file.
What’s the problem? Thanks in advance.

It could be a bug or by design to prevent sandboxed applications from being able to write to external media even with the external drive added to the “Do Not virtualize access to these files/folders” exception list.

You must copy the USB drive on the desktop.
Then copy the file
Warning the file is not available after stopping the virtual office.