Automatic Private IP Addressing (APIPA) is a Windows feature that assigns a DHCP-enabled network connection an IP address in the range 169.254.x.y in cases where a DHCP server is not available to allocate a legitimate IP address. Designed as a stopgap measure in case the DHCP server is only temporarily off line, a system with an APIPA address will attempt to contact the DHCP server to obtain a valid address at regular intervals.
While APIPA has its uses, some administrators would rather it not exist at all. The good news is that disabling APIPA for a given network adapter is easy enough via a Registry edit. Just follow these steps for a Windows XP Professional system:
1. Click Start > Run. Type Regedit.exe and press OK.
2. Browse to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\Adapters
3. Double click on the IPAutoconfigurationEnabled entry, and change its Value data to 0.
4. Close Regedit and restart.