declare @dbName varchar(32)

select @dbName = 'MyData' /* INSERT YOUR DATABASE NAME HERE */

/* Limit the database access to dbo's */
exec sp_dboption @dbName, 'dbo use only', 'true'

/* Remove existing users from the database */
exec spKillUsers @dbName


/* and here's the sp to kill them all */
/* COPY AND PASTE TO CREATE THE SP */
create procedure spKillUsers
@dbName varchar(32)

as
declare @spid smallint
declare @cmd varchar(32)

create table #tmp ( 
	spid smallint,
	status varchar(32),
	loginame varchar(32),
	hostname varchar(32),
	blk char(8),
	dbname varchar(32),
	cmd varchar(255))

declare cLogin cursor for select spid from #tmp where dbname = @dbName

insert into #tmp exec sp_who

open cLogin
fetch  cLogin into @spid

while @@fetch_status = 0 
begin
	select @cmd = 'kill ' + CONVERT(char, @spid)
	print @cmd
	execute( @cmd )
	fetch cLogin into @spid
end

close cLogin
deallocate cLogin

GO

grant execute on spKillUsers to public