NAS drives

I hope this is the right forum.

I'm helping a friend with setting up his home network. He has two desktop
PC's; one running Vista the other running Windows 7. Had a bit of
difficulty getting the windows 7 PC accessing shared folders on Vista PC
(but not the other way) but this has been resolved. I'm left now with one
issue and that relates to the Network Attached Storage (NAS) device that has
been connected to his router. What is required is a way to prevent or
block access to this drive from his daughters laptop which is running
Windows 7. He wants her to have internet access of course but not be able
to access his to desktop PC's or NAS drive. Her laptop is in a different
workgroup to his desktops which takes care of desktop PC access. How does
one go about preventing access to the NAS drive ??