Several Microsoft applications require databases that utilize the Windows Internal Database aka SQL Server 2005 Embedded Edition. These include WSUS 3.0 and WSS 3.0 (SharePoint Services). The instance is noted by a name of ‘MICROSOFT##SSEE’.
If you ever need to get at the databases contained in the instance you will find that this isn’t conventional. In SQL Server Management Studio UI you must use a named pipe identity in order to connect to this instance. You optionally could also use SQLCMD or OSQL scripts.
- Download and install the SQL Server Management Studio Express (if no SQL management tool is available)
- open SQL Server Management Studio Express **As Administrator** (if in a newer OS where that is an option)
- Connect the SQL Instance using named pipe
- Server name: ‘\\.\pipe\mssql$microsoft##ssee\sql\query’ (no quotations)
- Server Type: Database Engine
- Authentication: Windows Authentication
- options -> network protocol: Named Pipes
***now months later I found this critically important to a SharePoint installation that was using this database instance. What had occurred is that this separate and experimental lab server doesn’t have a regular backup routine; consequently, SQL’s log grows and grows until a backup is made. My _log.ldf file was well over 30GB! Also, the drive was less that 1% from full. So a little Googling and up popped an Experts Exchange thread that had the information embedded – http://www.experts-exchange.com/Microsoft/Development/MS-SQL-Server/SQL-Server-2005/Q_23983391.html With the Express Management Studio GUI and a couple of clicks it was all sorted. 
Lots of space released and I’m wiser for it.
a nice SQL reference: http://blogs.mssqltips.com/forums/t/843.aspx
***editors note***
As I worked through an SBS 2008 migration, the Companyweb migration instructions specify to ONLY open AS ADMINISTRATOR (right click the shortcut) the SQL Server Management Studio Express (SSMSE) before entering the Named Pipe path. DO IT. Trust me, if you don’t you won’t connect to the …##SSEE database.
