Default Windows 8.1x64 drivers issue

Hi all guys I need some help because i'm working on that since half an hour and I cant solve it.
I bought a new pc with windows 8.1x64 as operating system. I plug my TF300T and it don't recognize it. In the device tree it is marked with a yellow triangle and when i try to update the drivers manually installing them from the directory where I store the .inf (which work perfectly under windows 7x64) it returns me an error message saying that the .inf file is written for a win95 or newer operating system.

can you help me to fix this?

I already tried out the method illustrated in TF300T troubleshoot thread here on XDA where they suggest to disable the driver signature enforcement
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