Microsoft Audit Connection Service (ACS) is a new function in SCOM 2007 that can collect logs from machines. All logs are saved in a special Audit Collection database. You can then run reports against the database to see trends and do security analyzes. You can also trace a user over many systems. In SCOM 2007 beta 2 scenarios.doc there is a number of scenarios, if you would like to test ACS (2.5.2 Audit Collection) you will have to change connection string to  data source = FASQL01; initial catalog = dbAudit 

FASQL01 is the SQL server and dbAudit is the database. You replace the connection string under Home/Audit Reports/Db Audit in SQL reporting.