Preview file in 2 pieces
 

I have downloaded about 16% of a 40 MB non-avi file but can only preview 1 sec of this file. I've observed that this is the only file in the directory of partially downloaded files which is actually in 2 different files, 1 a small portion (the 1 sec that I can preview) and the other a much larger portion that I can't preview. Is there any way to join these 2 files?

Thank you.