One user account not working correctly
If you just need file access but don't need to be able to log in as that user you could just change the file permissions of the nutty users home folder.

Logged in as admin navigate in the Finder to the nutty user's home folder.

Select a folder you would like to be able to access (Desktop... Documents etc) and Get Info on it (Command + I).

In the resulting Info window in the "Sharing &amp; Permissions" section hit the plus button and select the group "Administrators" (or a named user if you prefer) and give this group (or named user) "Read only" access (or Read &amp; Write if you prefer).   Then under the little gear select "Apply to enclosed items"

Repeat for each folder you want to access.