KB96140 for SQL Server 2008, it's effectively the same process, just that it looks different to 2005.

This is from supportnet - KB88695 - It stops poeple connecting to the sims server... except the server itself :D (I have the sims client installed on the server to test with)

How to force Users out of Sims.net KB88695
THIS SOLUTION CANNOT BE USED FOR HOSTED SQL INSTANCES
The following workaround will terminate any current connections to the SIMS SQL Instance, and if users are actually using SIMS .net, this will force them out.
Any unsaved changes will be lost.

Please set the Surface Area Configuration of the SIMS SQL Server to Local Connections Only.
This means that only applications that use the SIMS SQL instance on the Server, itself, will be able to connect.
This will stop the user refresh from logging into the database when trying to upgrade, and allow SOLUS, DBupgrade, and DBAttach to complete successfully.

To re-configure this, please do the following:
Click Start
All Programs
Microsoft SQL Server 2005
Configuration Tools
SQL Server Surface Area Configuration

Click Surface Area Configuration for Services and Connections

From the instance list, please click Remote Connections under the Database Engine for the correct instance (ie SIMS2005)
Click Local Connections Only (The 1st radio button)
Click Apply

Click OK to the message

Click the Service
Click Stop, Click Start

This will stop the Users from connecting to the Server outside of the actual box
Run the specified application as required

When complete, please do the following
Click Start
All Programs
Microsoft SQL Server 2005
Configuration Tools
SQL Server Surface Area Configuration

Click Surface Area Configuration for Services and Connections

From the instance list, please click Remote Connections under the Database Engine for the correct instance
Click Local and remote connections
Click Using both TCP/IP and named pipes
Click Apply

Click OK to the message

Click the Service
Click Stop, Click Start