Not sure if this is the right place for this but when u watch some videos why do some of them stop during it and something it it sits and spins cozing the video to stop on occassions for whatever amount of time then resumes playing? What cozes it and is there any way to prevent it from doing it? It is a major PITA.
If you play from CD/DVD, it could simply be the Media like PRINCO etc! It could also be that the problems lies in the Video files. If later is the case, transcoding to a different format, like from AVI to MP4 or other, could solve the problem! Possible is also a Hardware fault, like the V-RAM on your Video Card, or the Chipset on it! There many things to check out and I would firstly start with Transcoding if everything works well on your Video Card!