User Groups in Vista

I want to change the security settings on a file (my personal finances) so that only my Admin account has access. However, by default the Users group has read access. If I set that to DENY, then my Admin account cannot read the fikle; apparently Admin users are part of the Users group, and the Deny policy in Users group overrides the Read policy for Admins.I'd like to remove Admin from the Users group, but I cannot find the way to modify Groups.I tried the trick on the Vista website about running MMC and adding the 'Local Users and Groups' snapin, but Vista says that the snapin cannot be used with Vista. Anyone have any suggestions?Thanks, Jason