Caution Do not use Services in Control Panel to change user account information.
Changing user account information through Control Panel results in a mismatch of
account information between the MSSQLServer and MSSearch services, and causes full-
text catalog population and querying to fail.
If a mismatch of user account information between the MSSQLServer and MSSearch
services occurs, ensure that both the MSSQLServer and MSSearch services are running.
Then, launch SQL Server Enterprise Manager. Using the Properties option and the
Security tab as described earlier, change the password for the MSSQLServer service.
Changing the password for the MSSQLServer service implicitly updates the account
information for the MSSearch service.
This info is also in BookOnLine under the topic of Installing SQL ServerRunning SQL
Server SetupBefore InstallingCreating SQL Server Services User Accounts:
Important If full-text search is installed on the computer, do not change the
MSSQLServer account information in the Services application in the Control Panel. While
the Microsoft Search service is always assigned to the local system account, it keeps
track of the MSSQLServer service account. You must change the MSSQLServer service
account in SQL Server Enterprise Manager for the Microsoft Search service to stay in sync.