How to reset a site to its profile installation? D7 I installed the Commerce Kickstart distribution and I've made some modification. Now I'd like to reset the site to remove all my modification and get the site restored.

Do I need a module to do this? Maybe this one: http://drupal.org/project/drupal_reset
Yep. You can also check out Demo as it is very very much helpful during testing and playing around in local development. You can create a snapshot of a clean website with your settings and then do whatever you want; if necessary with a click you can roll back to the initial settings without reinstalling the whole site.

Keep in mind though that you can use and setup Demo only before you start playing around - it will save the current site in a snapshot.