App installation traces befor uninstalling

Here's the thing, I download a 100 MB app, install it save some preferences, then uninstall it. Days later, install it again: This is what chagnes, 1st: Didn't download it again, because it took 20 seconds to install so: Where are this files saved locally? 2nd: The preferences didn't reset so: Where are this preference or config files stores?

I checked the WindowsApp folder on Program files where all the Metro apps are and it doesn't seem to be anything there.

Any help with this?

....... yes, it would be nice to know how to uninstall an app without leaving any traces behind.