ESET provides a dedicated web form for users who have lost their credentials.
While some third-party software claims to "extract" these keys from your registry, the most reliable "exclusive" methods are those provided by ESET themselves. The Safest Ways to Recover Your ESET License Key eset key finder exclusive
Note: This usually shows the License ID rather than the full activation key, which is useful for support tickets but not for activation. Why You Should Avoid "Exclusive" Third-Party Key Generators ESET provides a dedicated web form for users