You may also find, as I did that, the two halves of the case are glued together. My Fellowes P500 shredder doesn't shred properly, only creasing the paper. Deciding that, if I couldn't fix it, I would bin it, I prised it apart despite hearing ominous cracking sounds. After cleaning out all the paper strips, I reassembled it. NB. It needs the screws tightened to pull the halves completely together. It still won't shred so in the bin it goes. My next shredder WILL NOT be made by Fellowes in China or otherwise.
Bwriter, October 2006