Possible to 'reset' anything I've done in terminal?

[Summersify]

Hello,
I've had a Mac for quite a long time. In that time i've messed around with things like terminal a lot. What I want to do is 'reset' everything that I may have changed using terminal, so it's back to how it would be with a fresh copy of OS X Lion (so everything is back to its default, not including the things I can change in System Preferences).

Is this possible to do? I'm assuming that with OS upgrades it doesn't write over all of those changes. Am I just better off copying all my documents and applications onto an external hard drive and starting again?

I'm a bit OCD with my Mac like that

Thanks,
Jack

 

[maflynn]

The only way possible was to back up any files you changed prior to making the change and/or recording the values before you altered them. Short of that, reinstall is your only option.

 

[Summersify]

So OS upgrades won't write over settings like what's written at the log in screen?