I have the same problem, and, after looking at several other forums (fora?), I have just joined this forum as I am unable to find the answer. I have a Dell Optiplex with an Intel PRO/1000 MT and am connected to a Netgear DG 834G v2 Wireless modem router. Everything was running fine on Win2k and then I "upgraded" to XP. About 3 weeks later I was suddenly unable to connect to the internet; IPCONFIG shows the famous 169.254.239.91.
I thought it would be easy to start the configuration on the Netgear but am unable to connect to it on 192.168.0.1.