After installing SQL Server 2005 or Express on Windows Vista you may have noticed, that your user accounts (even though being in the local computer's administrators group) are not allowed to connect to the SQL Server. Which is bad if you're not running in Mixed Mode...

With the newly released Service Pack 2 for SQL Server and SQL Express there is a new tool available called "User Provisioning Tool for Vista"
(%ProgramFiles%\Microsoft SQL Server\90\Shared\sqlprov.exe).

This tool is automatically launched on upgrade (but can be started manually as well, if any errors occur at the first time). The small app tells us that, even if users are in the local administrator group, the don't have admin access to SQL Server for security reasons under Vista. You can use this tool to explicitly grant admin permissions to the current user (if it is in the local admin group).

God bless this tool :-) Now I am able to login again...