Well... If you plugged an iPod to a Mac (I assume this is what you meant by PC), it will automatically mount on your Mac desktop like any other regular Firewire hard disk. This is what people meant by putting the iPod into hard disk mode.
I think that the same thing also happen to the newly release Windows version of iPod.
As for being able to read the content of your iPod.
When it's in hard disk mode, you can read what ever files that were saved under hard disk mode. However, under hard disk mode you can't read the playable audio files
Note: There's a hack somewhere that will allow you to read both hard disk data files and playable audio files. It's not officially supported though.
As for being able to move your music from the iPod into the computer.
Unless those music files are saved under hard disk mode, you can't transfer them from the iPod to the computer. For the reason I mentioned above.
Note: Music files saved under hard disk mode can't be play by the iPod.
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