NTP support under Windows has always sucked, and likely always will suck. For one thing, it only really supports SNTP. It can sorta pretend to be an NTP server for other hosts on your network, but it screws up the stratum (it always sets it to the same number, regardless of its source), which screws up trying to use it with any other NTP server. It also isn't very accurate. It only stays within a few seconds of the real time, which is lousy. Good enough for government work, but, really? That's the best they could do?