sa's password in SQL Server 2008 R2 Express

Hi,

In the SQL Server 2005 Express I can chose  the expert mode during the installation. This enables me to set the password  of the user “sa”.

Now I tried to install SQL Server 2008 R2 Express but I had no possibility to change / set the password of the user “sa”.

I read in the internet that the default-password of the user “sa” should be a blank password. Since in SQL Server 2008 R2 Express there was no way to set / change “sa”’s password I tried to login with a blank password. But this also didn’t worked.

So my questions are:

1.    Where during the SQL Server 2008 R2 Express setup can I set / change the “sa”’s password.
2.    Where in the SQL Server 2008 R2 Express can I set / change the “sa”’s password after the installation.
3.    What’s the default password of “sa” in SQL Server 2008 R2 Express?
4.    Why a blank password for the unmodified “sa” account didn’t worked? 

Thank in advance for all your helpful answers.