Luc wrote:
I get an error message : 0800B0100.

I tried to contact MS but did not got an answer that solves my problem.

I tried to install SP1 in save mode as administrator but at the end the
installation fails with an "helpfull" message : look at
http://go.microsoft.com/fwlink/?linkid=10139.

Do you mean this Administrator account, because that's the only one on
Vista that has full admin rights at all times? Your user/admin account
you got out the box on Vista is not a user/admin account that has full
rights. Any new user/admin accounts that you will create will not be a
user/admin account with full rights either. There is only one admin
account that has full admin rights, Administrator.

http://www.howtogeek.com/howto/windows-vista/enable-the-hidden-administrator-account-on-windows-vista/

You should try going into safe mode using Administrator and see what
happens.