Thanks for the help and Yes, tech, I did install guarddog and it looks like a possible culprit here. Not understanding the dhcp settings in the advanced section of the program, I have disabled it for now.

When I first had issues I did upgrade the firmware on the router. It is a linksys. No PC uses IP 192.168.1.1 that is router's address, the gateway. I manually set up the ip address on the spare PC to use 192.168.1.101 in both linux and windows there. Windows on it has other issues left over from dialup and I plan to reimage those partitions.

Main PC so far has been getting correct IP. Still using DHCP both linux and windows on it. Lease I think is up any minute now so we will see. Lease setting is 0 which linksys says is one day. I didn't see any point in making it longer since if the IP is available, DHCP should dish it out again, no? The aggravating part of this is after one "use" it won't reuse it. Like it isn't being released or something? I am probably too networking-dumb or something but I have seen plenty of machines of customers merrily using DHCP in windows and not "running out" of addresses. So maybe a linux thing and in particular iptables (guarddog is just a front end after all).