Standard user accounts can access files of other accounts??!!

Hi,

I'm the only administrator on our home PC (Windows Vista Home Premium). The
rest of the family has been set up as standard users.
I read in the help files that standard users can't access files and folders
of other users. That's true for direct access through the folder structure.

However.... when searching for files with the help of the index, files and
folders of other users show up, and can be easily accessed even from standard
users.

Have I missed some kind of setting to restrict access of files and folders
between users, or is this a bug?

Best regards,
Ralf