janjust wroteif you bridge two adapters both get the same IP; what you really want is an IP alias for your ethernet adapter, which I am not sure windows supports....
Sorry, don't agree. But re-reading my post I still wasn't entirely clear.
What I am looking for is a network adapter, completely in software, which uses the physical network adapter to communicate. To do this, of course, the software driver would need to assign itself a MAC address different from the existing LAN adapter. Seen from the outside, the computer would actually seem to have two NICs, seen from the operating system level it would also have 2 different NICs, but in reality only one physical network adapter would be present.
Such NIC emulation software is possible, and was around for XP (virtnet driver), but I found none for WIndows 7 so far.
Armin
Btw, Windows supports additional ("helper") IP adresses on one interface, but this is not what I need.