The easiest way to do this might be to change to use Windows Authentication when connecting to SQL Express. Try changing your SI4 ini file as follows -
[MSDE]
DataSource=InstanceNameofSQLExpress (normally MachineName\SQLExpress)
Authen=Windows
SharedFolder=\\dtools-server\BizMgr (should be same as earlier)
Basically you have to change
1. Your DataSource to the SQLExpress instance name (normally MachineName\SQlExpress). Here MachineName is the name of the machine where SQL Express is installed.
2. Change Authen to Windows.
With Windows Authentication you are connecting to SQL with the currently logged on user in Windows and this should work if the SQL Server is on the same machine as the one you are trying to connect from.
The other method is to create a SQL user and password for the databases you restored - we can try that if this does not work. This is a little more complex.