Thank you for your answer.
From what I understand (sorry I'm very new to microcontrollers) I have to reboot to a known configuration, are you talking about baud rate? How do I do that? Is there a setting I should change? Tomorrow a friend is going to let me borrow his arduino to test it on my computer. I'd like to say that I tried it also on my other laptop and had the same error, blinking sketch wouldn't load giving me the same message.
And yes I made sure I selected the correct board (UNO) and the correct (and only) port.
Thanks again for your help