Mysql – PHPMyAdmin works with https Only (not http)

I've been having a problem getting phpmyadmin to work consistently on my XP desktop and laptop computers for months now. When I type into Chrome's browser on both machines, localhost/phpmyadmin, I kept getting Error #1045 Access Denied for user at root@localhost (using password yes).

Eventually, I realized that I had two (2) versions of mysql installed (XAMPP and MySQL Server 5.1) on both machines. So I uninstalled the MySQL Server 5.1I from the desktop and phpmyadmin worked. But when I uninstalled MySQL Server 5.1 from my laptop, it did not work. But I realized I could still get into MySQL Commandline Client using my password and that my databases were still intact. So I uninstalled and reinstalled XAMPP on the laptop and phpmyadmin worked after that.

Now I have a new problem. On phpMyAdmin's home page has a message at the bottom:

Your configuration file contains settings (root with no password) that correspond to the default MySQL privileged account. Your MySQL server is running with this default, is open to intrusion, and you really should fix this security hole by setting a password for user 'root'.

So I located the following lines in config.inc.php file:

/* Authentication type and info */

$cfg['Servers'][$i]['auth_type'] = 'config';

$cfg['Servers'][$i]['user'] = 'root';

$cfg['Servers'][$i]['password'] = '';

$cfg['Servers'][$i]['AllowNoPassword'] = true;

and I just changed the last 2 lines as follows:

$cfg['Servers'][$i]['password'] = 'mypassword';

$cfg['Servers'][$i]['AllowNoPassword'] = false;

As soon as I did that and I tried to access phpmyadmin again, I got the Error #1045 message again, but when I tried https://localhost/phpmyadmin/ I got a red page saying this sites certificate is not trusted would you like to proceed anyway. And now it only works using https.

I would really like to settle all my phpmyadmin problems once and for all so here are my questions:
1. Why does my laptop only access phpmyadmin via https?
2. How do I change my password in my configuration file?

Also, if you have any other tips regarding phpMyAdmin, they are very welcome. Thanks in advance