[PHP][/PHP]The Utility can be running on WinXP/Vista/8, Win 8.1 excluded... As I know, TP-LINK driver is not compatible with Windows 8.1 very well... You'd better install the chipmaker's driver for...

Bandwidth Control is designed to minimize the impact caused when the connection is under heavy load. It cannot make the voice data have the highest priority for the whole network like QOS.

On web interface of R600VPN and Advanced Security page, did you uncheck Block Ping Packet from WAN Port?

You are trying to open port 3389 for 10.x.x.7 on ER604W and access it remotely via remote desktop connection, right? Protocol is TCP? WAN IP is public?

Your extender is WA830RE? The firmware is up to date? Can you connect to LAN port of the extender and try to download the file? Did you test and compare the speed connecting to the root router...

How did you configure the range extender and confirm it has been configured successfully? Follow the guide below to do troubleshooting. http://www.tp-link.com/en/faq-691.html