Check and kill the session connected in SQL Server Database

SQL Server Management Studio 2005

When you right click on a database and click Tasks and then click Detach Database, it brings up a dialog with the active connections.

By clicking on the hyperlink under “Messages” you can kill the active connections.
You can then kill those connections without detaching the database.

SQL Server Management Studio 2008
The interface has changed for SQL Server Management studio 2008, here are the steps

1. Right-click the server in Object Explorer and select ‘Activity Monitor’.
2. When this opens, expand the Processes group.
3. Now use the drop-down to filter the results by database name.
4. Kill off the server connections by selecting the right-click ‘Kill Process’ option.