"Are you running the video from the same drive as the rest of the system ? "
Yes
"What do you use to view the video ? "
Video LAN player
"Does it help if you exclude the player ?"
Now I exclude the player
"Do you also happen to use bittorrent at the same time? "
Yes, Emule e bittorrent
"Do the files you download go to the same drive where the video files are ?"
No, in another drive.
Closing Emule and Torrent seems to be better.
Today I test
Thanks for your help