Located the following names missing from a security key that allows network access. This was on a Windows Domain, but someone had removed these security settings.

administrators;aspnet;backup operators;everyone;power users;users

Administrators; Backup Operators; Everyone; Users

below are a few notes i ran across while looking this up

http://support.microsoft.com/kb/823659

http://www.techsupportforum.com/file-application-sharing/73592-xp-pro-share-logon-failure.html