Need to "unshare" drive

Running Vista Home Premium on a desktop into which I've just installed
a new drive . . . and I'm trying to restrict access to that drive to
just one user. (There are two user accounts, the one for which I'm
trying to restrict access is a Standard account.)

First, I successfully hid this drive following the instructions here:
http://www.howtogeek.com/howto/windo...windows-vista/

Second, I changed sharing ("right click"|Properties|Sharing|Advanced
Sharing|Permissions) to deny access to the standard account . . . and
from this account I still have full access. I also tried adding Deny
permissions to folders on this drive; I still have access to these
from this Standard account.

I do need to share this drive across a router-based network with an XP
computer. What must I do to maintain access on the older computer,
yet restrict access to the one user on the newer computer?

Thanks -