No drivers for Windows 10.

What's the browser do you use?Try different web browsers.

When connection drops, how did you make it work again? Go to Network---LAN Settings, change DNS server to 8.8.8.8 and Secondary DNS server to 8.8.4.4. Besides, you can try to disable UPnP.

That's weird... Wired connection from TD-W8968 to the laptop works OK? Remove the network profile on your Windows 7 when the router is off. http://www.tp-link.com/en/faq-281.html And then, power on...

The USB HD goes to sleep even if it is plugged in USB port of your PC?

Sounds like DLNA compatibility issue. As I know, TD-W9980 doesn't use standard DLNA module, which may cause the problem like yours.