http://msmvps.com/blogs/laflour/archive/2009/02/05/sharepoint-tip-9-do-you-know-when-server-name-is-used-in-account-pattern-of-a-new-web-application.aspxWhen you are configuring a new application pool and assigning the user account, you need to specify just the <username> for the ApplicationPoolUserName field only if SharePoint is the part of workgroup. In case of SharePoint as the part of ActiveenCommunityServer 2008.5 SP2 (Build: 40407.4157)