ESET’s customers can recover a lost Username and/or Password by entering the email address used to purchase or activate the software or the Username, below. To find your username, open the ESET Smart Security or ESET NOD32 Antivirus main program window and click Update → Username and Password setup. Your username will appear in the License details window.
Follow the following link
http://go.eset.com/us/support/lost-license