wc4trailer.avi is the trailer for the Wing Commander IV computer game. 
This file is available as part of the WC4 demo available at ftp.ea.com. It 
is contained inside a resource file called MOVIES.TRE.

wc4trailer.avi is a standard AVI file that uses the XAN video and audio 
codecs. This directory also contains a Win32 binary library named 
xanlib.dll which is capable of decoding Xan data.