Update central adminstration application pool system account

During the setup, SharePoint don’t ask you to choose a System Account to run the central adminstration application. By default the CA run under the setup account (Server Administrator). This can be a security issue and not a best practice. You change the application pool identity using this command :

stsadm –o updatefarmcredentials –identitytype configurableid –userlogin [DOMAIN\USER] –password [PASSWORD]

For more information :

http://technet.microsoft.com/en-us/library/cc288300.aspx