SQL SERVER - If noone has Sysadmin rights or SA password is lost?

Go to pproperties of relates servers from SQL Server Configuration Manager. Advanced->Properties than put "-m" parameter. Carefull about you have to put ";" after last parameter and put no space! I mean ";-m" (Without quotes).
Restart to SQL Server. Server will run in single mode.
Run SQLCMD.EXE as administrator. Give Sysadmin rights to your Windows user which you use at login for your SQL Server:
EXEC sp_addsrvrolemember "myserver\myuser","sysadmin";
GO


or

EXEC sp_password NULL, 'newpwd', 'sa';
GO

Don't forget delete parameter and restart server at regular mode!..

Source:
http://blogs.msdn.com/b/raulga/archive/2007/07/12/disaster-recovery-what-to-do-when-the-sa-account-password-is-lost-in-sql-server-2005.aspx