Further to the "bridged network" problem reported:
I have Virtual Box 4.3.24 installed on Windows 10 TP, both the 32 and 64-bit versions. Other than having to re-install VB after each new build update, it has performed well through and including build 9926.
After updating to build 10041, I received the following error message when I tried to start the Virtual Machine: "Could not start the machine Windoze XP because the following physical network interfaces were not found: Realtek PCIe GBE Family Controller (adapter 1). You can either change the machine's network settings or stop the machine."
I changed "bridged adaptor" to "NAT" and the Virtual Machine started, but it "could not connect all network drives" (or access the Internet).
I tried to switched back to "bridged adaptor", but the option is no longer available. It say there is no network adaptor. And Internet search indicated the solution to this condition is to repair install or [remove and] reinstall.
I tried a repair install followed by restart. It didn't help.
I tried to remove and reinstall Virtual Box. The "bridged adapter" option was now available, but the Virtual Machine won't start the VM because VB can't find Realtek Adaptor (which was the original problem)!!! Also, we no longer have any networking on the host computer, whether within or without the virtual machine.
I restored the host computer system from a backup, which returned me to the original problem described above.
I then downloaded Virtual Box 4.3.26, extension pack and guest additions! When I tried to install it, the installation hangs at ~ 80-90%. Can't cancel or restart without hard boot. And then, no Internet, no network, and no USB.
I restored the host computer system from a backup, and am waiting for a solution to this problem.
From these forums, it appears that build 10049 does not solve the problem, nor does VB 4.3.27.
Additionally, installing Virtual Box 4.3.26 on a Windows 7 machine also results in loss of networking, although uninstalling it solves the problem (unlike under Windows 10, where a system restore is needed). VB 4.3.24 can still be installed on Windows 7. This indicates that the problem everyone is reporting is not just a Windows 10 problem, but something in Virtual Box 4.3.26.
The problem described still exists with Windows 10TP Build 10061, both 32-bit and 64-bit versions.
The problem described still exists with Windows 10TP Build 10074, both 32-bit and 64-bit versions.
The problem described still exists with Virtual Box 4.3.28! Installing with Bridged Networking on Windows 7 or Windows 10 results in a loss of networking on the host machine. Installing it without bridged networking works.
When I get round to it, I'll let you know what happens, if I can