How do I switch between drupal user accounts for testing?

Original question...

I'm running drupal on my local server using localhost before launching. Is there a way to run 2 copies of drupal. I want to be logged in as admin user to make changes. But to view my admin changes, I want to be logged in as a regular (authenticated) user. When I tried to do a duplicate drupal access in another browser window, drupal kept only one of the logins.

It takes a lot of time to keep going back and forth between logins.

I'm obviously a newbie to Drupal (but not web apps).

Stephanie