Just to update, I finally found the updated Realtek drivers for my motherboard. Installing those has fixed the problem .
Motherboard: ASUS M5A99X-EVO-R20
I updated both the Realtek Audio and Network drivers.
I have on board audio and a Firewire Echo AudioFire4 soundcard. Both are recognised by Windows. MPC-HC plays to both. Reaper 4.78 reports: WDM: AudioFire4 DirectSound, WaveOut: Mix, Realtek, AudioFire4 ASIO: AudioFire4, JackRouter WASAPI: Realtek, AudioFire4 I was running Audacity 2.1.0. That hit th...