Are you running it as Admin? (right click shortcut and click Run as Administrator) As far as I've tried NiBitor always worked under Vista (with both x86 and x64 versions).
Tried that but didnt work, have recently read that it doesn't seem to work in Vista64.
Fortunatly i dual boot with XP Pro32 and it worked just fine, read my BIOS no probs. Just not sure how it works, im interested in OC'ing my card & wanted to try increase the voltage so i can push for higher clocks. Seem to be struggling cant get past 760Mhz on the core before the driver crashes.
I belive some people have volt modded this card and have hit over 800Mhz on the core, and loads more on the shaders and memory. Would love to try and achieve this as im skint and cant buy a new GFX so was hoping a big OC would keep me content with my performance for a little while longer