ADMINS - Multiple accounts on my PC

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When i started playing on Argonath i created 1 acc , /register  *pass*, but when i click /login *pass* it doesnt login
So i crated another one , and it worked , so i am playing with that acc
And before few days my friend created his account on my computer , without me knowing it (i was on other computer)

So i think there are multiple accounts on my IP , but i use only 1 ...so dont bann me , admins