Here is my setup for the network, and which pc is

Right now, I am disconnected from the router. Let me tell you the way it was BEFORE I messed up the router connection:
Cable modem to router. New, upstairs, pc to router, downstairs pc also to router, from cable running alongside the house. At the time, I could only get online through the upstairs computer. I could see each computer's shared files, but could not ACCESS the upstairs' files from the downstairs. The downstairs computer almost logged on, but then froze and the connection was lost. The taskbar said that the router was connected, and the router icon light was green, and the "port magic" software was connected. Then, after our discussion about ipconfig/all, I noticed that there was a line that asked if the router configured the ip address, and on both of the 2 lines, it said "no." So I got to thinking (my first mistake!) that maybe my brother-in-law had not really completed the router configuration (language barriers with him) and that I was logged on through cable, but bypassing the router, if it hadn't configured the ip address. So I tried to run the port magic configuration wizard again, but got stuck when I realized it was prompting me for numbers I didn't have (it was asking me to check with my ISP for the numbers). So I tried to get out of it and get back online, but by now I had somehow messed something up and couldn't even log on at all. Even after trying to reboot the modem and router, my router was listed as "unavailable" and the router icon on the taskbar was and still is a little red hat. So I plugged my upstairs computer (the one I am on now) directly back into the cable modem and got back online so I could register with the Netgear company to call tech support for the router. So all along, the only computer I have been able to get online with, one way or another, is the upstairs computer. When I called Netgear tech support, the guy had me start plugging the computer back into the router, into each of the ports, and trying to get those IP addresses. Now here's where I was getting 169's and zeros on the upstairs computer, but the downstairs computer was coming up with 192 IP's. So I plugged the upstairs computer back into the cable modem, and here I am. Whenever I try to connect the router, I am unable at this point to clear out whatever I did to lose the "green hat" icon and only have a red disconnect icon. I have never been able to get online downstairs; the only thing that is "working" there, is that since we've been testing IP addresses, that one is coming up with the correct numbers. Given that I am online now, through the cable modem, without a router, leads me to believe that my cable is fine. My brother-in-law had tested the cables before he left the other day and confirmed 100mbps on each of them. I am getting 172 IP addresses now upstairs while I am online. It is a question of why, with this computer, I am suddenly unable to get normal-looking IP addresses, and why I am unable now (where I had been able before) to get the router to "connected" status on the taskbar. Hopefully, Sunday morning, my brother-in-law (more of an electrician than a computer tech) is coming to check the connections for me again, and figure out what if anything I messed up. If you have any suggestions for us between now and then that will lead us to what to look for, that would be great... if not, perhaps I'd have more answers for you after he checks things at my end. He was unable to complete this set-up, though, so we may be back to square one, which would at least be better than after I messed it up.
Sorry it's so long, but maybe now you get the full picture.