When installing SharePoint 2010 on a Windows 7 laptop, Windows security system can create some unexpected problems.
My laptop belongs to a Windows domain. But I was not connected to the domain during the installation. The SharePoint setup program completed without any complaints. But when I ran the configuration wizard, it would complain that the user was not found in the SQL database.
I checked the SQL Express server. I could login as the machine's local administrator. But if I tried to run the configuration program as the machine's local administrator, I would get an error saying that there was a data error.
So I used the simplest solution: install everything as the machine's local administrator. Of course, I would have to adde the domain user into the SharePoint sites as an administrator afterwards.