If you have forgotten your admin password, you can change it directly in the database. You need a tool like phpMyAdmin to do this. In the xampplite environment, you call this up from your browser at http://localhost/phpmyadmin.
Select the database you are using. There is a jos_users table in this database. In it search for the user admin. The password is encrypted with the MD5 procedure. You can change it by selecting the MD5 entry in the options list on the left next to the field and entering the password in plain text.
Many providers also supply you with phpMyAdmin to maintain your database.