Change Service Accounts & Passwords for MOSS2007

For reference article microsoft

http://support.microsoft.com/kb/934838

run commands
stsadm -o updatefarmcredentials -identitytype NetworkService
iisreset

this didn't work for me even i changed the identity from IIS application pool property. no luck

FIX:

1. Go to Sharepoint Central Administration.
2. On the top navigation bar, click Operations.
3. On the Operations page, in the Security Configuration section, click Service accounts.
4. On the Service Accounts page, in the Credential Management section, under Select the component to update, select Web application pool.
5. In the Web service list, click a Web service.
6. In the Application pool list, click the application pool that you want associated with the Web application.
7. Under Select an account for this component, select one of the following:
8. Predefined. Select this option to use a predefined account, such as the Network Service account or the Local Service account.
9. Configurable. Select this option to specify a different account.
10. Click OK.

other references:
http://geekswithblogs.net/influent1/archive/2009/04/15/131231.aspx
http://ithinksharepoint.blogspot.com/2008/10/renaming-user-accounts-within.html