This issue happens sometimes for users that had the SQL Server installed before ADOit:CE and it is a SQL Server with Windows Authentication security.
This problem was fixed in ADOit:CE 1.1. In order to check what version did you download, please check the version.txt file (search in "installer\setup\BOC\ADOit CE\").
If for any reason you cannot use the new installation package please try the following:
The fastest solution is the installation of an additional SQL Server instance for ADOit:CE. This can be done either in automated way by using command scripts available below or manually (in this case simply use the properties from the cmd file).
a) Download the command file suitable for your operating system (see below for the attached files)
b) Copy the correct batch file to the sqlexpress folder of ADOit (assuming you extracted the ZIP file to C:\ADOit it will be C:\ADOit \ADOit_CE_1_0\sqlexpress
c) Double click on the CMD file
d) This will now install a new SQL Server instance "ADOITCE" with sa password a0Xi90EeKQ
e) Start the ADOit:CE setup again
During the database installation, select the instance ADOITCE and continue with setup