Before migrating the SCOM 2007R2 environment of a customer of mine, I wanted to correct the Action Account that was used by the Gatewayserver. Microsoft has a PowerShell script that allows you to set the action account on groups of computers.
it’s called “SC Ops Mgr 2007 Resource Kit – Action Account Tool” http://www.microsoft.com/en-us/download/details.aspx?id=14175
set-action.ps1 “domain\accountname”
For this environment it took 20 minutes for the script to run;
Computer: ‘gatewayserver.fqdn’ …changing action account
From: ‘domain\old_accountname’
To : ‘domain\accountname’