PLEASE HELP ME

I have downloaded few mpg files from limewire though the size of the file shows that it has been fully downloaded but when i play it in media player of VCD or any player it runs for a few minutes and then gets stuck and then when i try to fast forward it a few clips ahead run for seconds but the full movie doesnt run.What i fail to understand is that the movie has been fully downloaded it begins playing means there is no problem of compatibility but why the hell it runs only for a few minutes?

Any of you have faced this problem please help me.

GOD BLESS YOU.