Reset VPS to default

Hi, Noez De Community!

I have trying to install mail server, but after installation I have received many troubles with my website. After that I was gone to server panel and press on Reinstall system, but after reinstall list of installed packages not changed. All packages which I have installed before reinstallation was on my «new reinstalled ubuntu».

How I can reset my server to default? I want to reset all settings and clean all packages.