Until now, the USBASP windows driver wasn't signed. On older versions of windows this was't too much of a problem as you could override the signature error. On Windows Vista x64 and Windows 7, it is almost a show stopper.
Various methods have been suggested including a utility called Driver Signature Enforcement Overrider or Pressing F8 at boot time and selecting Disable Driver Signature Enforcement. These approaches were far from ideal.
With the release of libusb-win32 version 220.127.116.11 this is a thing of the past. A new USBASP driver is now available; is based on the libusb-win32 driver; and supports 32 and 64 bit windows. It is partially signed which means windows still produces a warning during installation, but that warning does not prevent installation of the driver.
OK, now for the installation procedure...
- Download the driver from http://www.protostack.com/download/USBasp-win-driver-x86-x64-ia64-v1.2.4.zip and unzip it
- For those having issues with the zip file, please try the following rar file http://www.protostack.com/download/USBasp-win-driver-x86-x64-ia64-v1.2.4.rar
- Insert the USBASP into your USB port
- The system will attempt to install a driver from Windows Update
- and will fail
- At this point, go into device manager and find the entry for the USBASP programmer. It should be displayed with a yellow alert icon next to it.
- Right click on the device and select "Update Driver Software"
- When prompted "How do you want to search for driver software", select "Browse my computer for driver software"
- Select the folder where you unzipped the driver files then click "Next"
- At this point, windows will give you a nice red warning dialog with the message "Windows can't verify the publisher of this driver software".
- Click "Install this driver software anyway" and the driver will install.