P8 is a 32bit program, so even if your laptop is 64bit, P8 -and every other 32bit program- will still be constrained to 32bit memory allocation.

If you are using Poser Pro, it will render in 64bit if you specify render in separate process.  Poser Pro 2010 will automatically run and render in 64bit.

The only other reason I can think of for the missing AVI texture in P8 would be that perhaps your laptop doesn't have the video codec in which the movies were compressed.  You could right-click on the AVI and check its properties to identify the codec used.

If you are rendering in 64bit (either Poser Pro or Poser Pro 2010), then it is almost certain that your machine does not have a 64bit counterpart to the 32bit video codec originally used to compress the movie.  If anyone knows where to find such codecs, let me know!

Please specify which version of Poser you are using.  I do have a 64bit workaround using a matrix in place of the movie node, but it has severe limitations as to number of frames and pixel dimensions of the frames.
Here is a setup for a four cell by four cell matrix (sixteen total frames looped) of lightning:

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5