I have the same issue. After I completed my registration, It says “The procedure entry point “SetDisplayConfig” could not be located in the dynamic link library user32.dll.”
I also have Vista 64 bits and I have no posibility of updating to Windows 7/8.
It is a bit of a shame that there was no refenrence at the website as I would not have bought it until support for it was fully stablished. I was quite happy while buying it just to throw all the expectations about Vorpx to nothing.
Bonus: I guess you could use ChangeDisplaySettingsEx instead SetDisplayConfig which should work in Vista/XP