Some older versions of ESET allow you to perform this conversion directly within the application interface.
Open your ESET product and select from the left-hand menu. Click Change License in the bottom right corner.
For both home and business users, several official paths exist to transition old credentials into the new key format:
This method requires an active internet connection and an up-to-date ESET product. ESET v15+ does not accept Username/Password at all; you must use this method on an older machine or perform a fresh install using the online installer.
To avoid losing it again, click the "Register" link. Enter your email address. ESET will send your new License Key to your inbox and attach it to your ESET Home account.