Wireless Routers

I need information on how to set up 2 computers using the same cable modem (modem equiped with 6 connections)with a wireless router. What distance will the router handle? Best way to set up? Both computers have network cards installed already. Also, do all the computers have to have the same version of windows installed on them? One has Windows 98 and one has WindowsXP. Any help will be greatly appreciated.