My first suggestion would be to
Re-download the driver package from here
http://www.trendnet.com/support/supportdetail.asp?prod=190_TEW-726EC
Use 7zip to extract the contents of the zip file and then copy
\Drivers\Win81x64 or \Drivers\Win8x86 to external media (CD, DVD, USB, whatever) depending on your system architecture 32 or 64 bit.
Then uninstall anything you've installed up to this point regarding software or drivers relating to the problem device especially any programs that came as part of the package.
Go to device manager, find the problem device, right click it and choose uninstall, if prompted, also select remove drivers.
Reboot.
Now use device manager to install the drivers from the media you created above, manually.
- Open the Device Manager.
- Right click the device you wish to change the drivers for. You can select Properties > Driver > Driver Details to check you have the right device.
- Choose Update Driver Software.
- Select Browse My Computer For Driver Software.
- Select Let me pick from a list of device drivers on my computer.
- Select Have disk...
- Select Browse..
- Navigate to the extracted folder and double click on the .inf file
- Hit OK, then Next and the driver(s) will then begin to install.