- Ensure that Windows Media Player is running before booting the receiver
- Ensure that the Windows service, "Windows Media Player Network Sharing Service" is ON
- Denon support recommends turning OFF UPnP on your router
- Check that your firewall is not blocking something needed
- Try restarting Windows Media Player and the Nework Sharing Service
However, after fussing around with the above and other tests, I still find that the Denon just very rarely locates my PC. However, it plays Internet radio, so it's got an OK connection to the Internet; it's just not registering my PC.
So...Enter Twonky. Twonky Media Server 4.9 or Twonky Media Manager 1.0 always find my PC music! Hooray!