Completely wipe off and reset router

Hello,

What is the correct method to completely wipe off and reset configuration of a MikroTik router?

I have tried system > reset configuration from the GUI / Winbox and also have tried to Do not backup option, but upon reboot, the FILES menu still shows files from before.

Yes - I can go and delete the files, but is there a way to do a complete wipe?

(Router was compromised by Hajime malware recently and would like to make sure it is COMPLETELY wiped.)

Best way is NetInstall