Never could get VOX to work on our test Vista box. Probably driver related. In debug, all the operating system functions return good status, there is just nothing to capture.
I know it works with some sound card/devices, but I have yet to hear anything consistent so we could make a list.
There could be some flag or control somewhere, but in all the support calls I have had about this, nothing logical has been found as to why some boxes work and others do not.
I'll accept any help on this as I have tried everything I think of to get our own test Vista box to work. It has a Realtek HD audio chip (not sure of the exact model number. I'll see if I can get that Tuesday).