"could see the other computer in NWM but not in My Network Places. "
again, dont use Network Neighborhood/places, it doesnt always work right.
If you have a share successfully setup on a PC (ie with the correct username/password) then from any other PC you should be able to go to Start>Run and type in \\OtherPCIPAddress\SharedItemName and have it open the shared item, that can be a folder, printer, etc
Having the router see the PC's isnt doing anything, since the router is whats giving the PC's the IP address, of course its going to see them.
Whats the shared item name you have setup on one of the PC's ?