One of my Windows 7 PCs on my Home network (which has 3 XP machines, 1 Vista, and 2 Windows 7 machines) started having the "Unidentified Network" problem. It wouldn’t connect to the already existing Home Network setup that it previously connected to fine. After some trial and effort and research, this is the following approach that worked for me:
First of all I checked CMD Prompt to see my current IP address using the command: ipconfig and it had 169.254.x.x which appears when the gateway fails to give the computer a correct address. Which should be something like 192.168.x.x (dependant on your network setup).
So I changed my adapter MAC address:
Device Manager >
Network Adapters >
Right Click on the network card >
Properties >
Advanced Tab >
Network Address and enter a 12-digit alphanumeric string (0 to 9 or A to F) in the value field eg 1234567890AB >
OK
Now open CMD prompt and type:
ipconfig /release
Enter
ipconfig /renew
Enter
Success! Now my pc is back on the correct network and I am able to stream movies to my other PCs again.
UPDATE: Microsoft has an article relating to this issue here. It looks like the issue goes back to Windows Vista not able to obtain an IP address from certain routers or from certain non-microsoft DHCP servers. I will update this post soon to show the 2nd option here.
