Admin Login not working!!

[yrepetto]

Release version: 1.5.x (installed 1/7/09)

Localhost – XAMPP 1.7.0

System Information: PHPmYaDMIN 3.1.1

OS: Windows Vista

Unable to login to localhost/joomlabeta/administrator - says I have wrong user ID and PW.

Attempts to solve:
- Web server and Joomla installations were successful.
- When trying to login in, receive error messages attached.
- Attempted suggestions in similar problem posted on 1/5 regarding the jos_plugin designation (published vs not published); mine was '1' already
- in the phpMyadmin I did a password change then was unable to get the admin login screen; instead the error 'database error unable to connect' (see attached)

I know how to get into the database and change the admin settings, but how do I get it to apply? I went from being able to get to a login prompt screen, and getting error that I did not have correct credentials, to no prompt and error message 'database error...' after changing my PW in phpMyadmin

[yrepetto]

I've since tried this:
- reinstalled Joomla (now I get the login in prompt, but still rejects login info)
- added new super user (without the underscore user)
- changed password
- added database privledges for msql and mydatabase
- reloaded dadatabse privledges at least twice

There was one suggestion to alter the var $lifetime setting in configuration.php, but I could not locate this file. Also, someone said the cause of the problem might have to do with the ZIP program. I believe I have whatever comes with Windows Vista (could not find anything in the All programs area that resembled a ZIP program. On right-click, then Send To, I get Compressed - ZIP Folder).

Please tell me the correct format for a username. The guide I used (above) had this format: username_user. Is it necessary to have the underscore "user"? If so, how would I enter it in the username field on the login prompt? Here are some combinations I used (none worked):

username_user
username_user@localhost
username
username@localhost
[email protected] (seemed logical; this was requested above the admin password field)

I have attached some screen shots for reference.