For some reason, you might forgotten your osCommerce administrator login detail or you no longer able to log in anymore.
To overcome this problem, you may refer to the following step,
1. Log into the cPanel and navigate to the PHPMyAdmin icon.
2. Select the database used by the osCommerce and go to the administrators table.
3. Click on the Empty button to purge the administrators table data. (Assume you have only one administrator)
4. Now, go to your administrator page and you may enter the new administrator username and password.