The unfortunate answer is no. By design, access to the device is only allowed through the Zune software. I'm actually surprised the registry hack even let you see the files on the device.
What I would try however with your device unplugged, go to Settings / Account / Computers and Devices and remove your Zune device from the list (not your computer, but your device).
Then the next time you plug the device in, you'll have to re-setup a sync relationship. If you leave it as a guest, it may allow you to sync the files.
Toffer Davidson
Zune Product Team
.: This posting is provided "as-is" with no warranties, and confers no rights :.