How to close existing connections to a DB

Found it here: http://awesomesql.wordpress.com/2010/02/08/script-to-drop-all-connections-to-a-database/

DECLARE @dbname NVARCHAR(128)
SET @dbname = 'DB name here'
 -- db to drop connections 
DECLARE @processid INT 
SELECT  @processid = MIN(spid)
FROM    master.dbo.sysprocesses
WHERE   dbid = DB_ID(@dbname) 
WHILE @processid IS NOT NULL 
    BEGIN 
        EXEC ('KILL ' + @processid) 
        SELECT  @processid = MIN(spid)
        FROM    master.dbo.sysprocesses
        WHERE   dbid = DB_ID(@dbname) 
    END

in restore wizard click "close existing connections to destination database"

in Detach Database wizard click "Drop connection" item.

This should disconnect everyone else, and leave you as the only user:

alter database YourDb set single_user with rollback immediate

Note: Don't forget

alter database YourDb set MULTI_USER

after you're done!