OK, well first do this go START>>RUN>>services.msc (enter)
This will bring up the services window, scroll down to DHCP, and set to OFF & Disable, then also go to wireless zero configuration, and do the same , then reboot. Do this on BOTH PC's.
Now BOTH PC's MUST have an Individual Name, Also MUST have a Login Name & Password, Also MUST be part of same Workgroup.
Now in the Router DHCP MUST be set to ON. Now that's about it. The Router, hands out the address to the PC's, To connect, it most likely now will simply connect, but if it doesn't simply run the connect to internet Wizard, chose connect via a Gateway, which is the Router/Modem unit. It works like this, The PC your using, broadcasts out that it is here, then the PC talks backwards and forwards to the router, and the router says, here is your address, your PC, says. great, now, I want www.bla bla bla, address, and the Router, then sends out a request on the internet for that address, it obtains that address if valid, and then routes it to your PC. So, if it's NOT working it is a simple matter to troubleshoot.
Now if you have screwed up you IP Stack, Winsock, then I also include a XP program that will reset all that back to how it first was, and should be. It is called WinsockXP. DO NOT just run it unless you are sure you need to, and all else has failed, as it will reset everything back to default. So if that's what you want to do, then fine.
Now you connect the router/modem to the net, the Ethernet cable into say 1 & 2 Ethernet sockets, connect to the internet from each one. Also always get at least two browsers of differing sorts, say, Firefox, IE, and Chrome, is a good choice, as if it will not work with some, it may with another browser.