USBDK is a free, open-source driver package for Windows that allows user-mode applications to directly access USB devices. It is commonly used by:
The official version is maintained on GitHub by daynix (formerly contributed to by virtio-win). The actual installer file is typically named usbdk-x64.msi (for 64-bit Windows) or usbdk-x86.msi (32-bit).
Solution: USBDK drivers are signed, but if you see an error:
A reboot is required to load the kernel driver fully.