Getting WIndows XP to release DHCP IP address from WIFI adapter?

Does anyone know of a way to get windows XP to release the DHCP IP address off of a WIFI adapter when it looses connectivity with an access point? I have a broadband dialup adapater for a backup connection, but my routing table doesn’t work unless the WIFI adapter lets go of the DHCP IP address after the SSID is no longer valid.

The WIFI is an Intel chipset, and it seems like it does work periodically, but not very often, for some reason.

Thanks for any replies!