|Run the following from a command line:|
netsh int ip reset c:\resetlog.txt
"Connect that machine directly to the modem and see if it get's an IP from the ISP. If it doesn't, it's something in the machine. If it does, it's a router problem."
Not a bright idea unless you've exhausted other measures, and you are certain a firewall is running and properly configured on your XP machine. Otherwise, you're worm food waiting to happen.
"Milk was a bad choice!"