Burning dvd's
 

I have a problem maybe somebody can help me with.....
I downloaded a movie it was in avi when I tried burning it to dvd it went from 700mbs to 3.78gs and the movie doesn't play in my dvd player, but in my gf's it plays but the picture is not clear and it is jumping.
Can someone tell me why it is doing this and how I can correct it?
I am using Nero to burn it and I have a I/O Magic Lightscribe Dual Format Double Layer dvd burner
I am new to burning and any help will do.....