SQL Server Agent Properties (Log On Tab)
Use the Log On tab of the SQL Server Agent Properties dialog box to specify the account used by the SQL Server Agent service, and to start and stop the service. Changing the password of an account takes effect immediately without restarting the service.
When changing the account name used by a service on a clustered instance, the new account must be a member of the domain group specified during setup for the service being changed, or you must have permission to add members to that group. If you do not have permission to modify group membership, contact the domain administrator.
Local System account
Specify a local system account, which does not require a password. However, the local system account may restrict the service from interacting with other servers, depending on the privileges granted to the account.
Specify a local or domain user account that uses Windows Authentication. Microsoft recommends using a domain user account with minimal rights for services. For information about selecting an account, search Books Online for "Setting Up Windows Service Accounts."
Specify the local or domain user account name.
Type the password of the account.
Type the password of the account again.
Start the service.
Stop the service.
Pause the service.
Resume a paused service.