My current Ethernet network subnet is 255.255.255.0

No, that's not your subnet. That is your SUBNET MASK, not your subnet.

The subnet mask tells the system which bits have to be the same for it to be part of the same subnet. So, your case, 255.255.255.0 means that when you have two computers with the address X.X.X.Q, the X.X.X is the subnet, and the .Q is the individual machines. In otherwords, a standard subnet range of about 254 addresses (0 and 255 being reserved for other stuff).

So, for example, if your DHCP server is serving up addresses in the range of 10.12.13.1 through 10.12.13.254, the subnet is 10.12.13 and the individual machines are numbered 1-254.

So if you want to put the HPNA on a different subnet, you would, for example, make the subnet for that card 10.12.14.

Finally, one thing you need to know that hasn't yet been mentioned in this thread...

Since you will be running this on an NT server, your first desire will probably be to run the Receiver server software as an "NT Service", which it won't do, at least not by default. In its default configuration, you will need to log in to the box before the server software runs.

If you want to run it as an NT service, the program "FireDaemon" will reportedly get anything running as an NT service, I haven't actually tried it though. Another option is to throw out the Receiver software completely and use a third-party version in place of it. The JReceiver server software runs in Java, reportedly works great, can run as a service, and has some nice features. Both of these options are linked in the FAQ forum of this bulletin board, I believe.