@kidkon
That's the most easiest to let my parents find out who changed the password, it is me.
@RoboC
Thank you so much bro, this reply is typing with my sister computer!
Now, just ask a question to all. How to delete the account I made? Because my sister account is locked. Of course, I can not log in to her account because I have no her password of the account.
My sister was went for college, every month or week, she will be back to home. I must pretend all of this to let her know I used her computer otherwise she will told my parents then I will be death.
[Edited after this reply posted after about 5 minutes]
Let me make a guess, should I type something like this?[ net user 12345 /del ], shouldn't I?
[Edited after about 30 minutes above that]
I found out how to delete it.
By the way, thanks for all helping.