I've been having problems with my XP computers in my small office network when they move from one network/subnet and DHCP server to another. If I connect a computer using DHCP to one network, then move it to the other network, I can connect, but it won't pull down an IP. I keep getting "DHCP server unavailable" when I run ipconfig /release and ipconfig /renew. The "repair" option in the GUI doesn't work either. It's as if windows XP doesn't realize that there is a new DHCP server on the network. It insists on trying to renew an address in the old address range.
I've also tried "netsh int ip reset" in hopes that it would reset some setting that ties a particular network interface to a DHCP server or address range.
I've had this problem on 4 laptops now. My workaround has just been to only connect wirelessly to one of the networks, that way I never have to renew an IP in a new subnet and with a new DHCP server. In one instance, I actually had to swap out the wireless network card with another to get windows to connect happily to a new wireless network.
I've heard from other IT friends that this is a common windows XP problem but I haven't been able to find an elegant solution online (ie: something other than changing hardware or reinstalling the OS).