restricting certain users on a network to access file..

i have 2 PC's & 2 laptops connected via a Belkin Wireless G- Router...only the laptops are connected wirelessly. for ease i am referring to the PC's as A & B & the laptops as C & D...on A i have enabled sharing of a drive..now this drive is visible to B, C & D all under "my network places"...but i want it to be visible to only B...so that C & D can't access it...is there any way to do it?