A windows 8.1 compatible Windows Driver
When I upgraded to WIndows 8.1 I found that the existing USBTinyISP 220.127.116.11 Drivers were throwing up errors when I attempted to install them. The error I got was "attempt to load a program with incorrect format windows"
This is a quick set of drivers created the latest version of libusb-win32 (18.104.22.168) and used the included inf-wizard tool to create new drivers for the USBTinyISP.
I installed them with the Windows 8.1 with disable driver signature enforcement though as I understand it this should not be required to do this. I used the update driver tool in Windows device manager to install the driver. I have left the installation programs in place but they are untested.