Got it working.
I think the root cause was that windows media player was not installed (I am in Europe so it is not installed by default).
I then removed the android ADB drivers that I had added, removed the flash drive in device manager, and reconnected the Nexus. At that point it was re-detected, and windows 8 asked me what to do with it (open in explorer in my case).
All appears fine now!
Sent from my Nexus 7 using Android Central Forums