Quick update for those complaining about USB adapters. The issue is the more commonly available Belkin type adapter. They stopped updating drivers back in the Vista days.
The alternative is the Keyspan Tripp-Lite USB to serial adapter:
http://www.amazon.com/Tripp-Lite-USA-19HS-High-Speed-supports/dp/B0000VYJRY
Wintec4 has work flawlessly on my Tec3r using this thing, both in Windows 8.1 and now Windows 10.