Just a very quick note about this.
I upgraded my laptop to 64-bit Windows 7 a week or so ago and have just gotten round to setting it up for AVR programming. I thought for a while that I'd never get my USB programmer to work (AVRStudio couldn't auto detect my AVR ISP even after installing/reinstalling). After a little bit of searching I found this thread on avrfreaks.net. I followed the directions, allowed windows to discover the correct drivers at the end of the process and, badabing-badaboom, everything now works fine (other than the fact that I installed a 32 bit Eclipse that isn't happy...).