Follow The instruction,
1.Go to the Start Menu in task bar
2.Go to the Control panel
3.Click on the User account
4.Again click User account
Then find Administrator account and guest account
Click on administrator account where you find these option
Chane my name
Create a password
Change a picture
Change account type
Setup my account to use >NET passport.Then you just click On
"change my name"
And change your administrator name.
If you feel any problem then contact with me.