Because you are being asked for a username and password, as far as windows is concerned you have no internet connection.
Did you re-install windows from scratch or simply copy everything from your old HDD to your new HDD? If you re-installed windows from scrath what your symptoms are pretty much exactly what I would expect to happen.
Firstly (just to check), go through this brief process (although I imagine you already have). Turn computer off. Unplug cable modem (power cord and cable cord). Wait 5 seconds. Plug modem back in. Turn computer back on.
If this fails it sounds like you may have to re-setup your LAN connection in internet explorer by going to tools and internet options. If you dont know how to do this give BY tech support a ring and they will talk you through it. I suggest you do this anyway, because your problem sounds like a fairly simple one to me. Its just there are various processes you need to go through to check some things that take too much explanation to describe here. All of which BY can talk you through.