I must really check things more before i post in this forum.
Well it was not the computer name. It's the name of my first username.
I cant change it bcz when i am loged in on my own username i cant change the bcz it's being used. Then i tried with another loggin that also was admin but it didn't work. You can stop try to help me bcz i will get a new computer...
Anyway thanks for helping me!