Not sure exactly what you mean - when you attach the new USB adapter, it shows up as a new Wi-Fi entry. The biggest pain that took a while to figure out was that I had to remove my home access point from the "known networks" of the built-in adapter and then re-add to the external. Before that, it would refuse to connect on the external without any reason why.
I'm currently using this adapter - you can find it on sale for ~$65:
Also tried this adapter and it worked well. I returned it when I saw the d-link on sale. The other issue with this one is it doesn't support DFS channels which I use in my network: