Was given a RouterBoard 450. Help me reset it

Hello
I was recently given a RouterBoard 450. The person who gave it to me knew nothing of it, but knowing I am “in the computers” he gave it to me.

I have connected via serial to it and tried to log in but obviously I don’t have the passwords.

I need help to reset it. I have tried installing the Mikrotik upgrade software on WIndows but I didn’t seem to be able to make it work.

On a Cisco I know you just have to enter rommon and delete the startup_config file. From what I understand this isn’t the case for Mikrotik and it requires a complete reinstall of the firmware.

I hope this doesn’t require another license.

EDIT:
I have managed to update the bootloader via xmodem but it still does not show up on netinstall

I have solved the problem

I was using a Windows 7 machine. To make it work I had to run Netinstall in compatibility mode as Windows XP SP2