The SQL-Server database could not be opened Dynamicweb

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The SQL-Server database could not be opened ('') - the error is:
System.Data.SqlClient.SqlException (0x80131904): Login failed for user ''.

Ever ran into this problem with Dynamicweb, and thought you had set up everything correctly?
Well, I had to set up IIS, SQL Server and a new local installation of Dynamicweb up on a new machine.

Installed IIS8 and SQL Server Express 2012.
I created a new website in IIS and pointed it to the application folder as well as a virtual directory for the files folder.
Edited files\GlobalSettings.aspx

<password>mypass</password>
<type>ms_sqlserver</type>
<username>myuser</username>
<database>mydatabase</database>
<sqlserver>.\sqlexpress</sqlserver>
<integratedsecurity>false</integratedsecurity>

I downloaded and restored the DefaultEmptyData8SQL.zip database from developer.dynamicweb-cms.com
Mapped “myuser” to the database and gave it following database roles: db_datareader, db_datawriter, db_ddladmin and public.

Even though, I still got this error.
One thing I forgot, was to enable “SQL Server and Windows Authentication mode”, as this was a new installation of SQL Server.

Here’s how to do it, if you didn’t enable it in the installation process:

Go into SQL Server Management Studio – Win+R type ssms [Enter]
Right click your SQL instance – mine is called “.\sqlexpress (SQl Server version number – User\PC-Name)
Click on “Properties”, Go into “Security” chose “SQL Server and Windows Authentication mode” and then click [Ok]

SQL Server and Windows Authentication Mode

You’ll need to restart your SQL Server for the changes to take effect:

Win+R – cmd [Enter]
Stop and start SQL Server (Express)

net stop mssq$sqlexpress
net start mssql$sqlexpress

Taadaa! :)