VM Fault Issues
  A particular task may require several pages in memory to complete.

  If the page swapped out is still required
    An additional fault occurs.

  Room must be made in another frame and the swapped out page retrieved.

  However, it is possible that the bumped page may also be needed.

  Thrashing - when a page swap triggers a cascade of additional swaps
    to reestablish all the needed pages.

    XP with only 128 Meg of memory on boot up > 4 minutes.
      With 256 Meg of memory < 2 Miniutes.

  Better systems attempt to have empty slots (frames) at all times.

  To do this, it will swap out old or less used pages while the system 
    is performing non-paging tasks, even if the frame is not immediately 
    needed.