I will strongly suggest to reinstall the OS. They extra time you will spend (few hours max) is not worth it the thousand hours you will spend debuging in future. You will never be able to isolate or asses that the previous installation is not affecting you.
Unless your case is very particular (e.g. You really DO NOT have access to the machine, etc... ), reinstall the OS and give yourself peace of mind.
Nice guide though @Geoffrey Shelton Okot