Welcome. Seems like you've just forgotten your
admin account data. There is no
admin account by default after installation.
YOU create it yourself right when you first try to login to
admin panel.
So, if you really created an
admin account and now you can't log in (I understood you so), try to truncate a mysql table called
{your_prefix}_
admins and then go to
http://www.openslaeditalia.helloweb.eu/admin.php. The system will ask you for creating a new
admin account. Create it and log in ;)
Also you may have changed
admin-file name during your installation. Check it inside config/config.php ($
admin_file variable). If there is something different from "
admin" try to change it so it's equal to.
Good luck!