I bought a new ATmega328 board and when i first plugged it in to a computer it worked fine. Then I tried another computer and the message "Serial port 'COM3' not found. Did you select the right one from the Tools > Serial Port menu?" came up, but the port serial tab is grayed out, so I tried in the original computer which had worked fine, and gave me that same message .
Also, when plugging the board, windows doesn't show any messages and the board doesn't show in device manager, but the LEDs in the board light up when connected. I have tried with a different USB cable.
Tanks in advance