I have successfully installed POS 2009 (Manager and SQL Express database) on Windows 2008 Server, using an Administrator user called posclient. The main POS 2009 installer laid down the database for me, I did not do a manual install.
How can I determine the SA password? I want to create a new posadmin user with the SQL Server sysadmin role that can be used to run backups and perform other administrative tasks, but my posclient user is extremely limited in what it can do.