How to Remove a User from a SharePoint 2010 Site Collection

1 - As a site collection administrator, click Site Actions –> Site Permissions.
2 - Click into any existing group (like site Owners).  The URL will be something like http://server/_layouts/people.aspx?MembershipGroupID=28.
3 - Change the 28 to a 0.  The list should now show you All People.
4 - Find the user who isn’t updating, click the checkbox by their name.
5 - Click Actions, Delete Users from Site Collection.