OM222O:
Did you even read the question? I was using the board to generate square waves to drive a stepper driver and an external 60 watt supply but that's besides the point, the main problem is the serial line which means I can't reprogram the board, the code that's already on it works perfectly fine
That's not what you wrote.
I will quote your original post, so that you can't change it and make me look like a fool.
Hello, I was using an arduino nano to drive a stepper motor and display something to the serial monitor every 0.1 seconds. I then tried to upload another code to it but it didn't work. I unplugged the board but as soon as connected it back, the TX led started flashing and after a few seconds windows gave me an error that the USB device is not recognized (I plugged the motor back in and the board is ok,because it started ti drive it again). I tried pressing the restart button but it didn't work, the board is stuck in trying to push serial data to windows. I had a similar problem with a LPC1768 where I unplugged the board while it was accessing a file and had to go through their guide to recover the board. what is the recovery process with an arduino nano?