Windows NIC in promiscuous mode?

Is there any way to easily set a NIC in Windows NT4/2K to promiscuous mode?

I want to prove a point to my boss, who knows jack about computer security. They want to have a list of all user passwords stored in a database on their computer, and I want to show them how easy it is to crack passwords with a network sniffer & brute force, thereby giving anybody access to the database on said boss's computer.
I've got a copy of LC4 from @stake, but it only shows info for requests to/from the specific computer that it's running on. I've got Ethereal on a Linux box which seems to show more, but still not quite everything under promiscuous mode, and doesn't save the file in a format that LC4 can understand.
I think it might be a problem in that the network is running on a switch, rather than a hub. Is there any way to make a switch think there are two computers with the same IP, and transmit everything to both....or for that matter, make it think the LC4 computer's IP is 255.255.255.255, so it receives everything, anyway?

Or is this something I need to talk to our network admin about?