Getting multi-channel audio from PowerDVD 12 via HDMI

In PowerDVD's audio options it has

1. decoded to PCM by PowerDVD
2. Non-decoded Dolby Digital/DTS to external device
3. Non-decoded HD audio to external device

Since it's connected to an Onkyo TX-NR609 receiver which has DTS-HD and Dolby HD, and I want the receiver to handle Bluray sound as well as apply Dolby Pro-logic II matrixing to stereo (mainly kids' DVDs), obviously it's option 3 I want.

But when I chose option 3, it came to the receiver as 2.0 channel, despite the receiver being capable of 192kHz 24 bit HD sound - even according to Control Panel ->; Sound -> NVIDIA HD Audio Device -> Properties -> Supported Formats

Found this post which mentioned the Windows speaker setup. Indeed, it was still on 2 speakers. Switched it to 7.1 and now the receiver says it's receiving 5.1 Multi-channel for DVD sources - good. However, music from Windows Media Center is now sent to the receiver as 5.1, with no sound on the centre or surround channels. Worse, the receiver won't apply Pro-logic, as it's already getting 5.1 channels thanks to Windows. Music sounds dull.

Found this post for XBMC and a similar one for WMC which I now can't find, which suggest setting Windows' Speaker Settings to 2.0 channel, and enabling multi-channel output in WMC/XBMC. This works perfectly - music comes to the receiver as stereo, and Cyberlink PowerDVD sends raw encoded audio to the receiver which does its magic.