Windows 8.1 wrong driver, force driver

My pixhawk is wrongly recognized by windows 8.1 as “Unknown USB Device (Device Descriptor Failed)” and I find no way to force it accept the “right” driver. even not starting in the mode for unsigned drivers, not by deleting the device and rescan, not by re-installing,. when isntalling the driver by “have disk” windows pretends “the best driver software for your device is already installed”…
maybe somebody can help?

Problem solved:
After trying everything possible with no luck, I just changed the USB cable and voilà the unknown device changed to properly recognised.
Both cables were brand new, one came with the Pixhawk, one came with the 3DR Radio. I never had that a cable was working half (supplying power, “talking” but not transmitting the real ID of the device).
I hope this can help somebody with the same bad luck on a a new cable.

This just did help me out.

Thank you very much for having posted it!