The USBASP windows driver was previously based on libusb-win32. The certificate on the base drivers have expired and the library has now been superseded by libusbK. Earlier today we packaged up the driver and uploaded it to the server. You can now download it from the location below.
This driver should work with version of Windows XP right through to 8.1 and the version 10 preview. (both 32 and 64 bit editions). Because the driver is signed, there should be no need to disable driver certificate enforcement or use Zadig.