I just received a PRS-600 that has been used. It's in good shape, but is missing the stylus (any idea on where to get a replacement?), and it won't allow me to adjust most of the settings, saying it is in Demo Mode.
I've read around a little, and found some related topics regarding the 505. I have updated the device to the latest firmware from Sony, and it's still apparently in Demo Mode.
I have access to a Mac and a PC, so whichever works best for resolving this, I have.