Auto-Config told you it was successful and presented a link to enter the scripts and create your user, however you get to the login-page instead. Entering no username and no password doesn't let you in.
Here's what you do: Make sure you have the config-files CHMODed to 777. Run admin.pl without any parameters again. If Auto-Config doesn't run again and it doesn't let you in, upload an unmodified config.pl so that it will run again. If Auto-Config starts again, the new settings have not been saved.
Read through the whole text Auto-Config displays and check if everything's right and if there are no warnings amongst the messages.
Especially check the server-path, if you don't know the correct one, ask your server-admin. If Auto-Config didn't find the correct server path, you can give Auto-Config a hint.
If necessary, upload
an unmodified config.pl again and run auto-config like that:
the server find the config-files:
If this didn't help you, there are maybe problems with locating the config-files. Try the suggestions described on this page.
Upload an unmodified config.pl again. Even if the scripts find config.pl and the password and username at the bottom of config.pl are set to "" you won't be able to log in as even an empty password is crypted so it will be a random combination of numbers and letters. If this is causing problems, you can deactivate encrypted passwords. This is not really a security-risk, visitors can only find out the password if they download config.pl using FTP, and if a visitor gains FTP-access to your site, Schlabo's Scripts are your least problem.
Either call auto-config like that:
Or open config.pl in a text-editor, scroll down to the bottom and change the line to:
$crypted_passwords = "on";
Now try running auto config or logging in to the scripts without a username and password. You can also manually specify the important settings like the server-path and the URL of the images, upload config.pl and log in.