I had originally this set up with two Linksys WR54G routers, but the one upstairs apparently started flaking out and then my brother said he couldn't connect to the downstairs wireless using the instructions I had left (which I wrote up as I did it and everything worked fine when I set it up).
They tried to "fix" it and made it so much worse, and this is really crazy considering that no one at any time had access to the admin settings on the routers but me. Mom's currently connected directly to the cable modem right now, and downstairs has no internet.
I want to give them as foolproof a solution as possible that gives them little room to screw up.
Wanted to upload a diagram, but no way to upload from here at work. Hopefully this is descriptive enough.
cable line in goes to cable modem
cable modem CAT5 ethernet connection to [1 - router or ethernet hub?]
direct CAT5 ethernet connection from  to Mom's PC (upstairs)
direct CAT5 ethernet connection to [2-router or wireless access point?] downstairs
2 laptops and PS3 Slim connect wirelessly to