Upgrading From 5.x-2.x -> 6.x-3.x

1) If FileField and ImageAPI are not already installed, disable ImageField.
2) Upgrade Drupal and contributed Modules to 6.x.
3) Run Update.php 
4) If FileField and ImageAPI are not already installed
  a) install FileField and ImageAPI 
  b) enable ImageField,  FileField, and ImageAPI.
  c) run update.php.