@MikeMoss I think Poser creates first the images and after the images are done, it creates a movie file like AVI or Mpeg4 for example.
The reason why you are unable to delete the image files might be that you have Poser still running.
Windows does not allow files to be deleted who are used in the cache of said Program, even if the actual process is done.
If you close Poser the cache will be erased and you have full access to the files again.

Hope that helped.