Today I upgraded my old Drupal 5 installation to 5.19. In doing so I also figured that I may as well upgrade it to version 6. So I downloaded Drupal 6.13 and followed the directions to a tee (logging in as "master" user, removing old files, etc.) before copying my old /site and /files folders.
Now when I go to mysite.com/update.php it forwards to mysite.com/install.php instead.
So I'm stumped why this is happening and I've been trying to find a way to just get it to update the database from 5 to 6 all day.