XP Network Sharing Help :(

Hi all I found an old archived thread but it didn't really help me so I thought I would post and try and get some help.

Essentially at the moment the way I have my network set up at dads work is that we have 4 computers, 2 outside in the factory, and 2 in the office. Both myself and dad need write access to a shared folder on the network so we can alter files, add files, delete files etc (typical of a full access user). But I'd like to set up the two machines in the factory to only have read access to the folder (they never need to change the files just access for working). I can set up user permissions on local machine itself but I can't seem to set permissions via IP, or computer name or anything like that. I have heard that setting the same username and password on the computers will often work but I didn't get write access this way.

Is there a simple way of limiting read and write access to certain machines? I'm relatively computer literate I think but I've only really done basic sharing before, I heard I could set up a domain which would be more useful but I don't know how to go about this. Any help would be greatly appreciated :s