I would like to add test user accounts to my SharePoint 2010 development environment. It is running on a Windows Server 2008 OS. I have test user accounts I’ve created at the windows level. IIS's Authentication/Windows Authentication is set to Enabled. When I try to add users/groups at the Central Administration level or from within the SharePoint site collection itself the user accounts do not appear in the Select People and Groups – Webpage Dialog listing.
If the machine is joined to a domain it ahould pull in the available user accounts from AD. If it is a standalone development environment (off domain) then local accounts ahould be available but the people detail will be limited since it is local users and groups. If this is a standalone try adding the AD role to the server and make sure that you disable the DC group policy otherwise SP services will break.
This is a great read for getting dummy accounts loaded. http://www.wictorwilen.se/how-to-use-powershell-to-populate-active-directory-with-plenty-enough-users-for-sharepoint