I have a Windows XP machine that has two IPs, one private and one public, but just a single NIC. I've done this using regedit, not from TCP/IP configuration window (doesn't work for some reason, forgets the secondary IP instantly). Windows however seems to lose the secondary and private IP. It just disappears after a while, but not immediately like when using the configuration window. What should I do so that Windows would not lose this secondary IP?

I use this guide:
http://www.petri.co.il/configure_tcp..._same_time.htm