OK, we just got this one figured out.
=> Download the 64bit Sql 2005 Express.
http://www.microsoft.com/downloads/details.aspx?FamilyId=220549b5-0b07-4448-8848-dcc397514b41&displaylang=en=> Stop all of your SQL services on the SBS 2008 server.
=> Start the install by running the SQLEXPR.EXE you just downloaded.
=> Click "Run Program" on the "Program Compatibility Assistant" pop up. We will be reinstalling SP3 after we create the database, but before we restart the services.
=> Read and accept the "terms and conditions" and click NEXT.
=> Click NEXT after the support files are installed.
=> Click NEXT on the Installation Wizard screen.
Ignore the "ASP.Net Version..." and "Edition Change Check" warning messages and click NEXT.
=>
IMPORTANT! On the "Registration Information" window, UNCHECK the box next to "Hide advanced configuration options" and click NEXT.
=> Click NEXT on the "Feature Selection" window.
=>
IMPORTANT! On the "Instance Name" window, make sure you select "Named Instance" and name the instance "AVAST", without the quotes, and click NEXT.
=> On the "Service Account" window, leave the radio button checked for "use the built-in System account" and clear the checkbox in the "Start services at the end of setup" section next to "SQL Server" and click NEXT. This is so the services will stay down so that you can install SP3 and not have to boot the server.
=> On the "Authentication Mode" window, select "Mixed Mode" and enter an "sa" password you can remember and click NEXT.
=> On the "Collation Settings" window, just click NEXT.
=> On the "User Instances" window, leave the box checked and click NEXT.
=> Now click NEXT on the "Ready to Install" window to install the new instance for Avast.
OK, now that you have the new Instance installed, you will need to download SQL Server 2005 SP3 from here
http://www.microsoft.com/downloads/details.aspx?FamilyID=3181842a-4090-4431-acdd-9a1c832e65a6&displaylang=en,
BEFORE YOU START ANY SERVICES.The file you download will have the same name, SQLEXPR.EXE, as the SQL install, but it will be about 1.5MB larger.
Run the SQL Server 2005 Express SP3 file to install SP3.
After the SP3 instal is complete
START ALL OF THE SQL SERVICES BACK UP.You should now be able to start your ADNM install and point to the instance you just created and create a database in that instance using the "sa" password you specified before.
And FYI on detectionin ADNM, I seem to have to change it to AD on just about EVERY server install I do.
Good luck and let me know if you have any issues.