The Windows version 6.3 of AvrDude comes with an error " libusb-win32 and libftdi not found", while the Sertag version (a 5.x clone with these drivers patched into it) are working.
I don't know why, I installed the FTDI drivers, but i assume you must recompile to include these drivers in the AVRDUDE.EXE file.
It must be possible to build a 6.3x version with these drivers included, in a way simulair to the sertag version, and include this in a nest release of the arduino IDE .....