So.... when you say "I forgot the answer of my secret question." Im guessing that you mean for your steam account. And from that assumption, Im guessing you have forgotten your password to log into steam... In the case
Contact steam telling them about your problem, when you contact them, be sure to include and serial keys you may have used to unlock a game, and credit card numbers, the games you own, etc, as proof that it IS your account.
If this is not the case, please elaborate your problem.
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