Hi guys, thanks for your answers.
I spent last 2 hours with http://www.norton.com/chat . Needed to escalate the issue, but a supervisor installed N360 wihtout having admin password and all features N360 features are secured on that PC. The only thing, since wihtout admin password, can't access N360 features reserved to admin user, as it would be expected. I don't know how he've done it, but installed passed even if UAC is ON (unfortunately I'd like to have it off since a long time).
Thanks for your help. Will look at suggested above eigthforum to see if i can be helped me to recover/reset admin password.
Or best, can someone suggest me a hint toward finding a third party software to reset my own PC admin password? I investigated many out there, but haven't find one that would be working on W8 or even less on W8.1.