Flash CS3 cannot open FLash MX 2004 files

Hi,

 I've got a simple .fla file created with Macromedia MX 2004, which I'm trying 
to open with Flash CS3, but I get 
 "unexpected file format" error (this is not a mistake, I'm trying to
open an 
older file with the current version).

 Is there anything I can do to diagnose what the problem is ? I'm new to Flash 
and am trying to assist a friend
 who's got the original MX 2004 file. He can open the file no problem on his 
machine but I cannot open it on my
 machine

 Any help would be appreciated.

 Cheers,

 Bonny