Permissions for user on network

Hi,
I'd like to share a folder only for a certain user on a LAN. I'm on Win7-hp and the user is on XP-h. But when I go to assign permissions, the Location field only allows choices from my Win7 machine. If I put the XP user's name in directly, it flags that error.

The Win7 user is an admin, and I've tried this with both an XP admin and user account.

Surely there is some way to do this? Or alternatively, is there some way to do this via subnets?

Thanks,
p.

The easiest way to do this is to set up a another standard User account on your machine then set up another seperate standard User account on the XP machine then share the special secret files between those two User accounts. This will keep anyone else on the network locked out of those file shares.

Chev, this doesn't seem to be helping me. When I go, as a standard user, at the folder I want to share, I still cannot access any other Permissions/Location but the Win7 machine.