What OS? (win 7? which version)
Has this machine had this problem with a different OS installed?
Are there other computers that you can use to test? (same cable/same router or switch?)
Check the event viewer for error logs, might help determine why it is dropping.
what you should try is to enter your bios and go to the page where you have the options for your lan controllers and disable the one you dont use, i have lan controller 1 and lan controller 2, i disabled nr2 in my bios because windows 7 seemed to want to use it even if it was disabled on the controlepanel in windows. so i had to disabled it from my bios and now it works just fine even iwth tcp/ip 6 ..just wanted to mention that too since many have suggested to disable tcpip 6, but that didnt help me at all..just set the lan controller you dont use in bios to off..worked for me atleast..
I would also try to post in Microsoft's Windows 7 forum for further assistance.
Microsoft does have an official Windows 7 RC Support Forum located here Windows 7 Category . It is supported by product specialists as well as engineers and support teams. You may want to post your question there.
Also, check out Microsoft Springboard for some great tips / tricks and other great resources.
If you do, stop it and disable it. It is actually the Bonjour DNS Responder Service, and I believe it is the cause of the "Unidentified Network."
The Unidentified Network disappeared after stopping this service and a quick disable/enable of the NIC, restoring Internet access.
I Actually just rebooted, edited this post, and then re-enabled the offensive service to see what would happen...Immediately after enabling the NIC and this bastard service, the "Unidentified Network" returned...stopped it, disabled it, disable/enable NIC...Internet back up and running and no "Unidentified Network." (woot - woot!)
Hope that helps! I haven't had issues since...
FYI - I experienced this in both build 7100 and 7127...I am running 7127 now x64 - and discovered this fix just last night...so far so good just rebooted and then edited this post...I believe this fix will solve 7100 build issues too; however... I have not tested 7100 again yet.
...I also re-enabled Win 7's Discovery Mapping services, but always leave IPv6 disabled just because I am not using it.
...another two reboots, and a hard disk addition, and no problems with the Internet! - If you tried another fix such as changing the address of your network adapter, under "Advanced" - this is not necessary...I set mine back to "Not Configured." Everything is working fine as long as the Bonjour service is not running...
Quad Core Q6600
4GB Corsair Dominator DDR2
NIC: Marvell Yukon 8E8056; driver v10.69.2.3 (4/21/2009)
***fyi - i did update the default Windows driver with this, Vista x64 driver
For the record, there is some blame pointing towards the following software, of which I do have installed and running properly:
Office 2007 SP2
Adobe CS3 (updated current)
I've found that when my net gets dropped, mmc.exe crashes or hangs when id try to disable the netcard. Simple fix: change one of the many settings on your netcard so that windows will automatically restart the netcard...thus refreshing your networking-similar to rebooting but staying in the same session.