lost file size coping over lan

I am trying to copy a 4.5 meg mpg file from a windows xp pro system to a windows 98 system. The files size on the destination drive is alway 1.5 megs. I accually is discarding the rest of the file. It is a movie file. I play it on the source system and it is complete 1.5 hrs. I play it on the destination system and it is 30 minutes.

Help