Re : howto reset tikiwiki
you seem to be pretty new to this kind of administration and I'm not sure what to answer, but this makes me think of something.
If you install tikiwiki in a new folder and don't run tiki-install.php, but tiki-index.php first, it will automaticaly try to find a DB if I remember right and that's probably why you ended up with it linked to your old DB. That's something you can fix by going to tiki-install.php, resetting database connection settings and then proceeding as for a normal install.