Why convert? Because a License Key is tied to the ESET License Administrator account, while a Username/Password pair works directly inside the software’s activation window, bypassing account login requirements. It is also the most reliable method for air-gapped (offline) computers.
If you can’t find your username, password, or your key, you don’t need to guess. ESET provides a recovery tool: eset convert license key to username and password best
To address your request, it is important to clarify that You cannot convert a modern 20-character License Key into a Username and Password. Instead, the process works in reverse: you must convert legacy Username and Password credentials into a License Key to activate newer versions of ESET products . How to Convert Legacy Credentials to a License Key Why convert